Imaging of 1-nm-thick films with 193-nm microscopy.

We have implemented a reflected-light microscope operating in the deep ultraviolet at 193 nm. Many materials absorb strongly at this wavelength, providing greatly enhanced contrast compared with visible and near-ultraviolet microscopes. Polymer films as thin as 1 nm and SiO(2) films as thin as 3 nm have been imaged with this nonoptimized instrument. We have also calculated image contrast for several thin-film materials that are important in semiconductor processing, and we show that 193-nm light provides 60-485x better contrast than visible light (500 nm) and 4-95x better contrast than near-ultraviolet light (315 nm) for these materials.

An adiabatic quantum electron pump

A quantum pumping mechanism that produces dc current or voltage in response to a cyclic deformation of the confining potential in an open quantum dot is reported. The voltage produced at zero current bias is sinusoidal in the phase difference between the two ac voltages deforming the potential and shows random fluctuations in amplitude and direction with small changes in external parameters such as magnetic field. The amplitude of the pumping response increases linearly with the frequency of the deformation. Dependencies of pumping on the strength of the deformations, temperature, and breaking of time-reversal symmetry were also investigated.

Glutaraldehyde: an alternative to formocresol for vital pulp therapy.

Based on the limited results of this eight-week comparison of formocresol and glutaraldehyde, it would appear that glutaraldehyde may offer distinct advantages over formocresol, in the treatment of cariously exposed primary and young permanent teeth. In particular, due to its chemical structure, it is more active in fixing the surface tissues and is more rapidly limited in its depth of penetration through these tissues. Glutaraldehyde does not exhibit as significant an ability to induce the total loss of vitality, in the radicular pulp tissues. The progression of formocresol treated pulps to apparent fibrotic replacement via granulation-tissue ingrowth, through the apex, does not occur with the glutaraldehyde-treated pulp tissues. There may, however, be a slow progression of fibrotic replacement of the glutaraldehyde fixed tissue, in the coronal portion of the radicular pulp. Perhaps most importantly it would seem that since the glutaraldehyde does not perfuse the tissues to the apex, it will not demonstrate systemic distribution and other extradental phenomena, as have been identified with the use of formocresol