An analytic expression is derived for the distribution G( R) of the end-to-end distance R of semiflexible polymers in external potentials to elucidate the effect of confinement on the mechanical and statistical properties of biomolecules. For parabolic confinement the result is exact whereas for realistic potentials a self-consistent ansatz is developed, so that G( R) is given explicitly even for hard wall confinement. The theoretical result is in excellent quantitative agreement with fluorescence microscopy data for actin filaments confined in rectangularly shaped microchannels. This allows an unambiguous determination of persistence length L P and the dependence of statistical properties such as Odijk's deflection length λ on the channel width D. It is shown that neglecting the effect of confinement leads to a significant overestimation of bending rigidities for filaments.

Head-disk contacts in a disk file with a rotary actuator are examined during loadlunload using laser Doppler vibrometry and acoustic emission techniques.A novel scheme that allows tracking of the slider with the laser beam of a laser Doppler vlbrometer during loadlunload is implemented. Head-disk contacts are found to occur as a function of the velocity of the slider along the inclined ramp prior to loading, and it is shown that a low vertical loading velocity is less likely to introduce head-disk contacts than a high loading v e l o c i t y .btroductiaOne way to overcome stiction and wear problems during startstop is to use a load/unload mechanism for the slider. Here, the head suspension assembly (HSA) is loaded onto the magnetic disk once it is spinning, and unloaded before the disk stops r&g, thereby avoiding stiction. With the elimination of stiction, texturing of the disks would not be necessary any longer, reeulting in smoother disks and consequently. lower flying heights.Although a load-unload mechanism would eliminate stiction problems, it is likely to introduce undesirable head-disk contacts. Jeong and Bogy [1,2] studied slider dynamics during l o a d h d o d using laser Doppler vibrometry and acoustic emission techniques to discem head-disk contacts. They concluded that the parameters controlling head-disk contacts are the vertical loading velocity and initial pitch and roll angle. Their load/unload mechanism consists of a specially designed linkage system that drives a bar which lowers and raises the head suspension assembly, thereby loading and unloading the slider [3]. While large form factor drives commonly use a linear actuator to position the read/write head, smaller drives employ rotary actuators since they take up less space. This study presents experimental measurements of the dynamics of the slider during loadiig performed on a 2.5" hard drive with a rotary actuator, and investigates whether or not Mdisk contact occurs during loading.

The relative effect of ramp profile and

The Contact Start-Stop (CSS) process commonly encountered in magnetic disk drives brings along with it problems of suction and wear, which are the main reasons for failure of the heaadisk interface. One solution to this problem is a load-unload mechanism. Here, the head suspension