o bjectives: headgears are among the effective orthodontic appliances to achieve treatment goals. unilateral molar distal movement is sometimes needed during an orthodontic treat- ment, which can be achieved by an asymmetric headgear. different unilateral headgears have been introduced. the main goal of this study was to analyze the force system of uni- lateral expanded outer bow asymmetric hea...

The authors demonstrate that the compositional sensitivity of an atomic force microscope is enhanced by the simultaneous excitation of its first two flexural eigenmodes. The coupling of those modes by the nonlinear probe-surface interactions enables to map compositional changes in several conjugated molecular materials with a phase shift sensitivity that is about one order of magnitude higher t...

Title of Dissertation: DEVELOPMENT AND APPLICATIONS OF MULTIFREQUENCY IMAGING AND SPECTROSCOPY METHODS IN DYNAMIC ATOMIC FORCE MICROSCOPY Gaurav Chawla, Doctor of Philosophy, 2011 Dissertation directed by: Assistant Professor Santiago D. Solares, Department of Mechanical Engineering Force spectroscopy and surface dissipation mapping are two of the most important applications of dynamic atomic f...

Cellulose nanofibrils (CNF) were spun into filaments directly from suspension without the aid of solvents. The influence of starting material properties and drying temperature on the properties of filaments produced from three different CNF suspensions was studied. Refiner-produced CNF was ground using a microgrinder at grinding times of 50 and 100 minutes. Filament spinning was performed using...

The authors present a method based on dynamic force microscopy to characterize subnanometer-scale mechanical vibrations in resonant microand nanoelectromechanical systems. The method simultaneously employs the first eigenmode of the microscope cantilever for topography imaging and the second eigenmode for the detection of the resonator vibration. Here, they apply this scheme for the characteriz...

The detection of higher modes of oscillation in atomic force microscopy can provide additional information on sample properties. However, the limited bandwidth of the photodiode in the beam deflection detection technique often limits the detectable frequency range. We present a novel cantilever design, which allows lowering the frequency of higher modes of oscillation, maintaining the frequency...

We describe contact-resonance atomic force microscopy ͑AFM͒ methods to quantitatively measure Poisson's ratio ␯ or shear modulus G at the same time as Young's modulus E. In contact-resonance AFM, the frequencies of the cantilever's resonant vibrations are measured while the tip is in contact with the sample. Simultaneous measurement of flexural and torsional vibrational modes enables E and ␯ to b...

In bimodal atomic force microscopy, two flexural modes are driven at their resonances. The oscillation of the second eigenmode, which is usually an incommensurate multiple of the fundamental frequency, perturbs the dynamic system. Numerical simulations show that the tip motion is almost periodic at typical set points and that harmonics and intermodulation frequencies prevail in the spectrum. Th...

Previous studies on adaptation of fingertip forces to local friction at individual digit-object interfaces largely focused on static phases of manipulative tasks in which humans could rely on anticipatory control based on the friction in previous trials. Here we instead analyze mechanisms underlying this adaptation after unpredictable changes in local friction between consecutive trials. With t...

Recent work gives a transverse force on an isolated moving vortex which is independent of the normal fluid velocity, but it is widely believed that the asymmetry of phonon scattering by a vortex leads to a transverse force dependent on the relative motion of the normal component and the vortex. We show that a widely accepted derivation of the transverse force is in error, and that a careful eva...