The Location of the Snow Line in Protostellar Disks

The snow line in a gas disk is defined as the distance from the star beyond which the water ice is stable against evaporation. Since oxygen is the most abundant element after hydrogen and helium, the presence of ice grains can have important consequences for disk evolution. However, determining the position of the snow line is not simple. I discuss some of the important processes that affect the position of the snow line.Comment: 8 pages, 5 figures. Invited talk at IAU Symposium 263 - Icy Bodies in the Solar System. Rio de Janeiro, Aug. 200

Gas accretion in galactic disks

Evidence for the accretion of material in spiral galaxies has grown over the past years and clear signatures can be found in HI observations of galaxies. We describe here new detailed and sensitive HI synthesis observations of a few nearby galaxies (NGC 3359, NGC 4565 and NGC 6946) which show that indeed accretion of small amounts of gas is taking place. These should be regarded as examples illustrating a general phenomenon of gas infall in galaxies. Such accretion may also be at the origin of the gaseous halos which are being found around spirals. Probably it is the same kind of phenomenon of material infall as observed in the stellar streams in the halo and outer parts of our galaxy and M 31Comment: To appear in the proceedings of the symposium "Extraplanar Gas", ASP Conference series, editor R. Braun, 8 pages + 5 figure

Engineered plasmon focusing on functional gratings

We report on the engineering of plasmon propagation and focusing by dedicated curved gratings and noncollinear phasematching. Gratings were created on gold by focused ion beam milling and plasmons were measured using phase sensitive PSTM

Phase gratings for plasmon focusing

We report gratings structures realized for the creation of focused plasmons through noncollinear phasematching. The gratings are created on gold by focused ion beam milling and the plasmons were measured using phase sensitive photon scanning tunneling microscope (PSTM)

High resolution imaging of dielectric surfaces with an evanescent field optical microscope

An evanescent field optical microscope (EFOM) is presented which employs frustrated total internal reflection o­n a localized scale by scanning a dielectric tip in close proximity to a sample surface. High resolution images of dielectric gratings and spheres containing both topographic and dielectric information have been obtained. The resolution obtained is 30 nm in the lateral directions and 0.1 nm in height depending o­n proper tip fabricatio

Star Formation and Gas Accretion in Nearby Galaxies

In order to quantify the relationship between gas accretion and star formation, we analyse a sample of 29 nearby galaxies from the WHISP survey which contains galaxies with and without evidence for recent gas accretion. We compare combined radial profiles of FUV (GALEX) and IR 24 {\mu}m (Spitzer) characterizing distributions of recent star formation with radial profiles of CO (IRAM, BIMA, or CARMA) and HI (WSRT) tracing molecular and atomic gas contents to examine star formation efficiencies in symmetric (quiescent), asymmetric (accreting), and interacting (tidally disturbed) galaxies. In addition, we investigate the relationship between star formation rate and HI in the outer discs for the three groups of galaxies. We confirm the general relationship between gas surface density and star formation surface density, but do not find a significant difference between the three groups of galaxies.Comment: Accepted for publication in MNRAS, 18 pages, 9 figures, 1 tabl

Influence of hole size on the extraordinary transmission through subwavelength hole arrays

We show that the extraordinary transmission of light through an array of square subwavelength holes is strongly influenced by the size of the holes. For small, square holes (air fraction below 20%), the dependence of the normalized transmission (transmissivity) on hole width greatly exceeds the expectations on the basis of conventional aperture theory. For larger holes, the transmissivity saturates. Moreover, the positions of the transmission maxima shift when the size is varied