Zinc-Nickel coatings, developed in the 1980's as a replacement for zinc coatings in the automotive industry, have recently gained interest in the aerospace industry to replace cadmium coatings. Due to different material properties of Zn-Ni and Cd, there is a need to characterize Zn-Ni for tribological applications. Sliding wear tests are performed on a reciprocating pin-on-flat tribometer using a steel counterface on two Zn-Ni coatings with different microstructure and surface topography. Tests were performed under 3, 7.5 and 12 N normal loads at a relative humidity of 60 % for 2000 cycles. Increasing the normal load increased the steady state friction coefficient and wear for both coatings. The smooth and dense coating was more sensitive to the change in normal load than the rough and porous coating, as the latter experienced less wear due to the columnar structure of the coating. In contrast, the smoother and dense coating, although has less wear at low loads, has more wear at high loads due to debonding of the coating. So the coating morphology affected the extent of wear due to different wear and velocity accommodation mechanisms.

Formation of nanocrystalline ZnO film on sliding wear tracks at high humidity levels reduces the wear.

Repair of radiation-induced dna double-strand breaks is a key mechanism in cancer cell radioresistance. The synthesized compound NU7026 specifically inhibits dna-dependent protein kinase (dna-pk) within the non-homologous end-joining repair mechanism. Earlier studies demonstrated increased radiosensitivity in dna-pk deficient cells compared with wild-type cells. In chronic leukemia cells, NU7026 appears to enhance the cytotoxic effect of chlorambucil. The radio-modifying effects of NU7026 on cell survival, cell cycle, apoptosis, and dna double-strand break repair have yet to be studied in gastric cancer cells. Methods: The gastric cancer cell line N87 was treated with 0 Gy or 4 Gy in the presence of NU7026 at a dose range of 0–20 μmol/L. Clonogenic assays were used to assess cell survival after treatment. Cell-cycle distribution was analyzed using propidium iodide with fluorescence-activated cell sorting. Apoptosis was detected using annexin-V and propidium iodide with fluorescence-activated cell sorting. The γH2AX assay was used to measure dna doublestrand breaks. Results: Statistically significant increases in G2/M arrest were observed in N87 cells treated with radiation and NU7026 compared with those treated with radiation alone (p = 0.0004). Combined treatment also led to an increase in apoptosis (p = 0.01). At 24 hours, the γH2AX analysis revealed more dna double-strand breaks in N87 cells treated with radiation and NU7026 than in those treated with radiation alone (p = 0.04). Clonogenic assays demonstrated declining cell survival as both the radiation and the NU7026 dose increased. The dose enhancement factor at 0.1 survival fraction was 1.28 when N87 cells were treated with 4 Gy radiation and 5 μmol/L NU7026. Conclusions: In gastric cancer cells, NU7026 appears to enhance the cytotoxic effect of irradiation as assessed by clonogenic assays. This increased cytotoxicity might be the result of an increase in dna double-strand breaks resulting in G2/M cell arrest and possibly higher levels of apoptosis.

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