Beta-titanium alloys are used in many industries due to their increased elongation resulting from their BCC structure and low modulus of elasticity. However, there are many limitations to their use due to the high cost of betastabilizer elements. In this study, biocompatible Ti-Mo-Fe beta titanium alloys are designed by replacing costly betastabilizer elements (e.g., Nb, Zr, or Ta) with inexpensive Mo and Fe elements. Additionally, Ti-Mo-Fe alloys designed with different Fe contents are fabricated using powder metallurgy. Fe is a strong, biocompatible beta-stabilizer element and a low-cost alloying element. The mechanical properties of the Ti-Mo-Fe metastable beta titanium alloys are analyzed in relation to the microstructural changes. When the Fe content increases, the tensile strength and elongation decrease due to brittle fracture despite a decreasing pore fraction. It is confirmed that the hardness and tensile strength of Ti-5Mo-2Fe P/M improve to more than 360 Hv and 900 MPa, respectively.

본 연구는 여수 인근 13개 무인도 주변 해역의 굴 Crassostrea gigas (n=410, SH 43.3±11.4 mm) 에서 확인된 인터섹스 현상을 보고하고자 하였다. 전체 성비(암:수)는 1:1.1이었으나 채집 정점 별로 성비의 차이를 보였다. 가장도, 소경도, 중삼도에서는 암컷이 65% 이상의 높은 비율을 보 였으며, 송도, 초도, 부서도에서는 수컷이 65% 이상의 높은 비율을 나타냈다. 전체 intersexuality 는 약 12.8%로 암컷에서 약 34.7%, 수컷에서 약 64.3%로 수컷에서 높았다. Intersexuality는 가막만의 초도에서 약 43.8%로 가장 높았다. 조직학적으로 인터섹스는 intrafollicular type, interfollicular type, mixed type의 세 가지 형태로 나눌 수 있었다. 이들 세 가지 형태 가운데 intrafollicular type이 약 81.6%로 가장 우세하였다. 본 연구에서 보고된 굴의 인터섹스 원인에 관해서는 추후 세부적인 연구가 필요할 것으로 생각된다.

Additive manufacturing by electron beam melting is an affordable process for fabricating near net shaped parts of titanium and its alloys. 3D additive-manufactured parts have various kinds of voids, lack of fusion, etc., and they may affect crack initiation and propagation. Post process is necessary to eliminate or minimize these defects. Hot isostatic pressing (HIP) is the main method, which is expensive. The objective of this paper is to achieve an optimum and simple post heat treatment process without the HIP process. Various post heat treatments are conducted for the 3Dprinted Ti-6Al-4V specimen below and above the beta transus temperature (996oC). The as-fabricated EBM Ti-6Al-4V alloy has an α‘-martensite structure and transforms into the α+β duplex phase during the post heat treatment. The fatigue strength of the as-fabricated specimen is 400 MPa. The post heat treatment at 1000oC/30 min/AC increases the fatigue strength to 420 MPa. By post heat treatment, the interior pore size and the pore volume fraction are reduced and this can increase the fatigue limit.

Titanium alloys have high specific strength, excellent corrosion and wear resistance, as well as high heatresistant strength compared to conventional steel materials. As intermetallic compounds based on Ti, TiAl alloys are becoming increasingly popular in the aerospace field because these alloys have low density and high creep properties. In spite of those advantages, the low ductility at room temperature and difficult machining performance of TiAl and Ti3Al materials has limited their potential applications. Titanium powder can be used in such cases for weight and cost reduction. Herein, pre-forms of Ti-Al-xMn powder alloys are fabricated by compression forming. In this process, Ti powder is added to Al and Mn powders and compressed, and the resulting mixture is subjected to various sintering temperature and holding times. The density of the powder-sintered specimens is measured and evaluated by correlation with phase formation, Mn addition, Kirkendall void, etc. Strong Al-Mn reactions can restrain Kirkendall void formation in Ti-Al-xMn powder alloys and result in increased density of the powder alloys. The effect of Al-Mn reactions and microstructural changes as well as Mn addition on the high-temperature compression properties are also analyzed for the Ti-Al-xMn powder alloys.

Titanium has many special characteristics such as specific high strength, low elastic modulus, excellent corrosion and oxidation resistance, etc. Beta titanium alloys, because of their good formability and strength, are used for jet engines, and as turbine blades in the automobile and aerospace industries. Low cost beta titanium alloys were developed to take economic advantage of the use of low-cost beta stabilizers such as Mo, Fe, and Cr. Generally, adding a trace of boron leads to grain refinement in casted titanium alloys due to the pinning effect of the TiB phases. This study analyzed and evaluated the microstructural and mechanical properties after plastic deformation and heat treatment in boron-modified Ti-2Al-9.2Mo-2Fe alloy. The results indicate that a trace of boron addition made grains finer; this refinement effect was found to be maintained after subsequent processes such as hot forging and solution treatment. This can effectively reduce the number of required manufacturing process steps and lead to savings in the overall cost as well as low-cost beta elements.

Expression of invasion/metastasis suppressor, E-cadherin, is reduced in many types of human carcinomas. Although somatic and germline mutations in the CDH1, which encodes the human E-cadherin, have frequently been reported in cases with diffuse gastric and lobular breast cancers, irreversible genetic inactivations are rare in other human carcinomas. Recently, it has been well documented that some genes in human cancers may be inactivated by altered CpG methylation. Herein, we determined the expression and methylation status of E-cadherin in oral squamous cell carcinoma(SCC) by immunohistochemistry and methylation-specific PCR. The expression of E-cadherin was significantly higher in the well-differentiated oral SCCs than the moderately or poorly differentiated ones. None of eight tested benign epithelial hyperplasias showed aberrant methylation, whereas five of 12 oral squamous cell carcinomas showed aberrant methylation. When we compared E-cadherin expression with methylation status, oral SCCs with normal methylation showed a higher expression of E-cadherin than those with methylation. These findings suggest that aberrant CpG methylation of CDH1 promoter region is closely associated with transcriptional inactivation and might be involved in tumor progression of the oral mucosa.