RESUMEN
Casing wear is a persistent issue in oil and gas drilling facilities that call for innovative more wear-resistant materials to mitigate casing failures. The present work examines the tribological performance of a novel composite lining comprised of Kevlar honeycomb in a matrix of epoxy reinforced with Zirconia particles against hardband drillpipe tooljoint (DP-TJ). Three side loads (1000, 1200, and 1400 N) and three DP-TJ speeds (0.43, 0.76, and 1.02 m/s) were considered under dry sliding conditions. The results showed that the specific wear rate (K) increased with speed at all side loads. However, K value was found to reach a maximum, reaching 20.3*10-8 MPa-1 at 1200 N before dropping to about 8.5*10-8 MPa-1 when the load is increased to 1400 N. This decline in specific wear rate at the load of 1400 N was attributed to the growth of a double transfer layer through the alignment of zirconia particles in the lining. The scanning electron microscope (SEM) images of worn surfaces revealed that higher K values are associated with more adhesion, delamination, and fiber breakage. Energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) analysis of the worn surface and the debris collected after the wear test reveals minimal wear of DP-TJ. The epoxy/Kevlar-honeycomb composite lining demonstrated appreciable wear resistance even under dry sliding conditions.
RESUMEN
OBJECTIVES: It is hypothesized that soccer players with periodontal disease exhibit raised serum creatine kinase (CK) levels as compared to those without periodontal disease. We assessed the clinical gingival status and serum CK levels among young soccer players. MATERIALS AND METHODS: Demographic data were collected through a structured questionnaire. Full mouth bleeding on probing (BOP) and probing pocket depth (PPD) were assessed. Blood samples (4 mL) were collected for measurement of serum CK levels. All blood samples were collected from a vein in the antecubital region. Total CK activities in serum were determined with an optimized spectrophotometric method. Statistical analysis was performed using one-way analysis of variance, and P< 0.05 was considered statistically significant. RESULTS: Twenty-seven male soccer players volunteered to participate in the present study. The mean age of the participants in Groups 1 (n = 14) and 2 (n = 13) were 18.2 ± 2.3 years and 19.1 ± 0.6 years, respectively. Mean scores of BOP were significantly higher among individuals in Group 2 (56.8%) compared with individuals in Group 1 (19.4%) (P < 0.001). Mean scores of PPD ≥4 mm were significantly higher among subjects in Group 2 (12.1%) as compared to individuals in Group 1 (0.8%) (P < 0.001). Levels of CK were significantly higher among individuals in Group 2 (292.7 U/L) as compared to those in Group 1 (52.3 U/L) (P < 0.01). CONCLUSION: Increased BOP and PPD are associated with increased serum CK levels in young soccer players.