Scaling and Confinement in Ultrathin Chalcogenide Films as Exemplified by GeTe.

Chalcogenides such as GeTe, PbTe, Sb2 Te3 , and Bi2 Se3 are characterized by an unconventional combination of properties enabling a plethora of applications ranging from thermo-electrics to phase change materials, topological insulators, and photonic switches. Chalcogenides possess pronounced optical absorption, relatively low effective masses, reasonably high electron mobilities, soft bonds, large bond polarizabilities, and low thermal conductivities. These remarkable characteristics are linked to an unconventional bonding mechanism characterized by a competition between electron delocalization and electron localization. Confinement, that is, the reduction of the sample dimension as realized in thin films should alter this competition and modify chemical bonds and the resulting properties. Here, pronounced changes of optical and vibrational properties are demonstrated for crystalline films of GeTe, while amorphous films of GeTe show no similar thickness dependence. For crystalline films, this thickness dependence persists up to remarkably large thicknesses above 15 nm. X-ray diffraction and accompanying simulations employing density functional theory relate these changes to thickness dependent structural (Peierls) distortions, due to an increased electron localization between adjacent atoms upon reducing the film thickness. A thickness dependence and hence potential to modify film properties for all chalcogenide films with a similar bonding mechanism is expected.

Isolated anisocoria from an endodermal cyst of the third cranial nerve mimicking an Adie's tonic pupil.

We present only the second reported case in the literature of a neuroenteric cyst involving the third cranial nerve. Our case is highlighted by the initial presentation of an isolated anisocoria, initially believed to represent an Adie's tonic pupil as interpreted by pharmacologic testing. False-positive results may occur with the dilute pilocarpine test.

Is addition of a third or fourth antiglaucoma medication effective?

PURPOSE: To study the intraocular pressure (IOP)-lowering effect of adding a third or a fourth antiglaucoma medication to preexisting antiglaucoma medical therapy, for a follow-up period of one year. PATIENTS AND METHODS: The authors performed a retrospective, nonrandomized, noncomparative, interventional study including all patients seen by a single glaucoma specialist at the University of Florida Eye Clinic between January 1, 2000 and December 31, 2000, who had a third or a fourth antiglaucoma medication added to their existing regimen of two or three antiglaucoma medications, respectively. The main outcome measured was IOP at 2, 6, 9, and 12 months after addition of an antiglaucoma medication. "Efficacy" success was defined as a decrease in intraocular pressure of greater than or equal to 20% from baseline, without a change in the antiglaucoma medical therapy. Also, "safety outcome" was analyzed based on the need for surgical intervention and/or the occurrence of intolerable side effects to the antiglaucoma medications leading to discontinuation of their use. RESULTS: Sixty-seven patients had a third, and 29 patients had a fourth antiglaucoma medication added to their existing regimen. Analysis for a specific time point showed a success rate of 48% at 2 months (n = 65), 47% at 6 months (n = 47), and 41% at 1 year (n = 39) after addition of a third antiglaucoma medication and 59% at 2 months (n = 29), 45% at 6 months (n = 22), and 55% at 1 year (n = 20) after addition of a fourth antiglaucoma medication. By Kaplan-Meier analysis the cumulative probability of achieving efficacy success (> or = 20% IOP decrease from baseline) was 33% at 6 months and 23% at 1 year after adding a third medication (Group A), and 43% at 6 months and 18% at 1 year after adding a fourth medication (Group B). Combining both efficacy and safety outcomes decreased the cumulative probability of success to 27% and 14% in Group A, and 31% and 14% for Group B, at 6 months and 1 year respectively. CONCLUSION: Addition of a third and fourth antiglaucoma medication produces a clinically significant reduction in IOP in about 40 to 60% of patients at any single time point. However, the cumulative probability of success including safety outcomes is relatively poor at 6 months and 1 year. This suggests that adding another antiglaucoma medication to a regimen of two or three medications frequently does not achieve a significant (> or = 20%) fall in IOP.