Detection of atomic force microscopy cantilever displacement with a transmitted electron beam.

The response time of an atomic force microscopy (AFM) cantilever can be decreased by reducing cantilever size; however, the fastest AFM cantilevers are currently nearing the smallest size that can be detected with the conventional optical lever approach. Here, we demonstrate an electron beam detection scheme for measuring AFM cantilever oscillations. The oscillating AFM tip is positioned perpendicular to and in the path of a stationary focused nanometer sized electron beam. As the tip oscillates, the thickness of the material under the electron beam changes, causing a fluctuation in the number of scattered transmitted electrons that are detected. We demonstrate detection of sub-nanometer vibration amplitudes with an electron beam, providing a pathway for dynamic AFM with cantilevers that are orders of magnitude smaller and faster than the current state of the art.

Specimen-thickness effects on transmission Kikuchi patterns in the scanning electron microscope.

We report the effects of varying specimen thickness on the generation of transmission Kikuchi patterns in the scanning electron microscope. Diffraction patterns sufficient for automated indexing were observed from films spanning nearly three orders of magnitude in thickness in several materials, from 5 nm of hafnium dioxide to 3 µm of aluminum, corresponding to a mass-thickness range of ~5 to 810 µg cm(-2) . The scattering events that are most likely to be detected in transmission are shown to be very near the exit surface of the films. The energies, spatial distribution and trajectories of the electrons that are transmitted through the film and are collected by the detector are predicted using Monte Carlo simulations.

Long-term oxygen therapy: advances and perspectives in technical devices.

Since the early beginnings of long-term oxygen therapy, by means of cylinders of compressed oxygen and their subsequent replacement with oxygen concentrators, most technical advances have been steadily focused on improving the facilities for continuous ambulatory oxygen therapy. Largely for this purpose, two different systems have been developed. 1) Oxygen concentrators in combination with portable cylinders for patients requiring oxygen at home and during short-term outdoor activities. If connected to an oxygen-conserving device, the duration of the ambulatory administration can be increased substantially. To improve mobility, a new generation of lightweight cylinders can nowadays be provided be several suppliers, thus; the weight of the portable systems can be reduced down to 2.1 kg. 2) Liquid oxygen is still the most convenient system for patients requiring continuous oxygen at home as well as during extensive daily outdoor activities. Liquid oxygen administration, however, is handicapped by its high costs, mainly due to logistical expenditure. Conserving devices are capable of lowering substantially the consumption and costs of gaseous and liquid oxygen. The following conserving techniques have proved to be efficient: reservoir cannulas, demand oxygen-pulse devices, and transtracheal catheters. The transtracheal route additionally improves physical ability and prolongs survival, suggested to be a consequence of unloading the work of breathing. Looking to future perspectives, there is ongoing progress in the technical improvement of concentrators. A very promising product is a new kind of concentrator which can be used to refill small portable cylinders at home. This system may be a real and probably less expensive alternative to liquid oxygen. In conclusion, all future efforts should be directed at improving the facilities for providing continuous ambulatory oxygen therapy, the superior concept for pulmonary rehabilitation in patients with chronic respiratory insufficiency.