The melting behavior of 0.1-10-nm-thick discontinuous indium films formed by evaporation on amorphous silicon nitride is investigated by an ultrasensitive thin-film scanning calorimetry technique. The films consist of ensembles of nanostructures for which the size dependence of the melting temperature and latent heat of fusion are determined. The relationship between the nanostructure radius and the corresponding melting point and latent heat is deduced solely from experimental results ͑i.e., with no assumed model͒ by comparing the calorimetric measurements to the particle size distributions obtained by transmission electron microscopy. It is shown that the melting point of the investigated indium nanostructures decreases as much as 110 K for particles with a radius of 2 nm. The experimental results are discussed in terms of existing melting point depression models. Excellent agreement with the homogeneous melting model is observed.

We report a study of the thermodynamic properties of indium clusters on a SiN (x) surface during the early stages of thin film growth using a sensitive nanocalorimetry technique. The measurements reveal the presence of abnormal discontinuities in the heat of melting below 100 degrees C. These discontinuities, for which temperature separation corresponds to a spatial periodicity equal to the thickness of an indium monolayer, are found to be related to the atomic "magic numbers," i.e., the number of atoms necessary to form a complete shell of atoms at particle surface.

We introduce a scanning calorimeter for use with a single solid or liquid sample with a volume down to a few nanoliters. Its use is demonstrated with the melting of 52 nL of indium, using heating rates from 100 to 1000 K/s. The heat of fusion was measured to within 5% of the bulk value, and the sensitivity of the measurement was ±7 μW. The heat of vaporization of water was measured in the scanning mode to be within ±23% of the bulk value by actively vaporizing water droplets from 2 to 100 nL in volume. Results within 25% were obtained for the heat of vaporization by using the calorimeter in a heat-conductive mode and measuring the passive evaporation of water. Temperature measurements over a period of 10 h had a standard deviation of 3 mK.

ABSTRACT:We used thin-film differential scanning calorimetry to investigate the melting of isolated polyethylene single crystals with lamellar thicknesses of 12 Ϯ 1 nm. We observed the melting of as few as 25 crystals. Over a wide number of crystals (25-2000 crystals), the heat of fusion was 40% larger than the bulk value. The melting temperature of the isolated single crystals was 123 Ϯ 2°C, 9°C lower than that of the bulk material. We also measured the heat of fusion of quenched crystals (Ϯ15%) over a wide range of heating rates (20,000 -100,000 K/s). Annealing the quenched crystals resulted in shifts in the endotherm peak by as much as 15°C.

As with many science fiction works, the Star Trek franchise uses allegory to address contemporary social issues. Taking a liberal humanistic stance, it addresses race and racism using aliens as allegorical stand-ins for humanity. However, the producers of the Star Trek franchise were inadvertently perpetuating the racism they were advocating against. Operating within the framework of normative Whiteness, the producers privilege the White American male as the average human being. The characters of other racial and cultural backgrounds try to assimilate into the normative Whiteness defined by the producers or they are simply in the background to support the White lead characters. By drawing on previous work on the original series and The Next Generation, this article examines episodes from Deep Space Nine, Voyager, and Enterprise to determine how the Star Trek franchise reinscribes, or sometimes destabilizes, the mode of racial and cultural homogeneity assumed by the producers.