The duration of the antiresorptive effects of the intravenous bisphosphonate, zoledronate, is not known. Recently, we reported that two annual 4-mg doses of zoledronate suppressed bone turnover and increased BMD in HIV-infected men over 24 mo. We set out to determine the persistence of these effects after two doses of zoledronate. Thirty-three HIV-infected men who completed a randomized trial of 4 mg annual zoledronate (n = 17) or placebo (n = 16) were studied for a further 12 mo, during which time no skeletal therapy was administered. Participants received calcium (400 mg/d) and vitamin D supplements (50,000 IU/mo) for the first 24 mo of the study only. Biochemical markers of bone turnover and BMD were measured every 6 mo. Bone turnover markers were stably suppressed at 24 and 36 mo (12 and 24 mo after the second annual dose of zoledronate, respectively). There were no significant within-group changes in urine N-telopeptide, serum C-telopeptide, and osteocalcin between 24 and 36 mo (p > 0.07), and at each time point, each of the turnover markers was significantly lower in the zoledronate group. There were also no significant between-group differences in the changes in BMD at each site between 24 and 36 mo, (p > 0.5), and at each time point. BMD at each site was significantly higher in the zoledronate group. These results suggest that the antiresorptive effects of zoledronate last > 12 mo and raise the possibility that zoledronate could be administered less frequently than annually. Randomized trials that address this issue should be performed.

This paper describes the methods used and results obtained from analysing some resonance phenomena which were observed on a steel railway bridge. These phenomena were visible on the slender hangers connecting the arch girder and the main truss girder under certain wind conditions. The paper describes the set up of a vibration monitoring system designed to measure the vibration response of the hangers together with the wind velocity and the wind direction over a period of several months under operational conditions. These data should yield the basis for correlating the wind and the structural characteristics. In addition artificial impulse hammer excitation was used to measure the modal characteristics (natural frequencies and modes of the hangers separately. The results of these tests compared well with those obtained from applying some "output only" modal identification techniques to the operational response data with unknown excitation forces. The results also compared well to analytical predictions and were used to identify the axial forces in the hangers by updating the axial force minimising the test/analysis deviations. The results allowed to estimate the fatigue life of the hangers confirming the need for the design of anti- vibration devices.