Effects of the bias enhanced nucleation hot-filament chemical-vapor deposition parameters on diamond nucleation on iridium

The effects of the bias current density and the filament-to-substrate distance on the nucleation of diamond on iridium buffer layers were investigated in a hot-filament chemical-vapor deposition (HFCVD) reactor. The nucleation density increased by several orders of magnitude with the raise of the bias current density. According to high-resolution field-emission gun scanning electron microscopy observation, diamond nuclei formed during bias-enhanced nucleation (BEN) did not show any preferred oriented growth. Moreover, the first-nearest-neighbor distance distribution was consistent with a random nucleation mechanism. This occurrence suggested that the diffusion of carbon species at the substrate surface was not the predominant mechanism taking place during BEN in the HFCVD process. This fact was attributed to the formation of a graphitic layer prior to diamond nucleation. We also observed that the reduction of the filament sample distance during BEN was helpful for diamond growth. This nucleation behavior was different from the one previously reported in the case of BEN-microwave chemical-vapor deposition experiments on iridium and has been tentatively explained by taking into account the specific properties and limitations of the HFCVD technique

Deep Near-Infrared Imaging af an Embedded Cluster in the Extreme Outer Galaxy: Census of Supernovae Triggered Star Formation

While conducting a near-infrared (NIR) survey of ``Digel Clouds'', which are thought to be located in the extreme outer Galaxy (EOG), Kobayashi & Tokunaga found star formation activity in ``Cloud 2'', a giant molecular cloud at the Galactic radius of ~ 20 kpc. Additional infrared imaging showed two embedded young clusters at the densest regions of the molecular cloud. Because the molecular cloud is located in the vicinity of a supernova remnant (SNR) HI shell, GSH 138-01-94, it was suggested that the star formation activity in Cloud 2 was triggered by this expanding HI shell. We obtained deep J (1.25 um), H (1.65 um) and K (2.2 um) images of one of the embedded clusters in Cloud 2 with high spatial resolution (FWHM ~0".3) and high sensitivity (K ~ 20 mag, 10 sigma). We identified 52 cluster members. The estimated stellar density (~ 10 pc^{-2}) suggests that the cluster is a T-association. This is the deepest NIR imaging of an embedded cluster in the EOG. The observed K-band luminosity function (KLF) suggests that the underlying initial mass function (IMF) of the cluster down to the detection limit of ~ 0.1 M_sun is not significantly different from the typical IMFs in the field and in the near-by star clusters. The overall characteristics of this cluster appears to be similar to those of other embedded clusters in the far outer Galaxy. The estimated age of the cluster from the KLF, which is less than 1 Myr, is consistent with the view that the star formation was triggered by the HI shell whose age was estimated at 4.3 Myr (Stil & Irwin). The 3-dimensional geometry of SNR shell, molecular cloud and the embedded cluster, which is inferred from our data, as well as the cluster age strongly suggest that the star formation in Cloud 2 was triggered by the SNR shell.Comment: 19pages, 8 figures, 1 table, accepted to ApJ. Full paper (pdf) with high resolution figures available at http://www.ioa.s.u-tokyo.ac.jp/~ck_yasui/papers/Cloud2N_1.pd

Efficiency comparison of three attractant products against webbing clothes moth Tineola bisselliella (Hummel) (Lepidoptera: Tineidae) using an adapted four arms olfactometer

Contribution to section 2: Biology, behaviour and detectio

The Effect of Star Formation on Molecular Clouds in Dwarf Irregular Galaxies: IC 10 and NGC 6822

We have observed the 13CO J=2-1, 12CO J=2-1 and 12CO J=3-2 lines at a few locations in the dwarf irregular galaxies IC 10 and NGC 6822 using the James Clerk Maxwell Telescope. In addition, we report the first detection of the 13CO J=3-2 transition in a Local Group galaxy. These low metallicity environments appear to be porous to UV radiation and allow for more efficient heating of molecular gas by nearby HII regions. The high 12CO J=3-2/J=2-1 ratio in NGC 6822 suggests that the 12CO emission is optically thin in this region. This high line ratio is likely the result of its location inside a large HII region with low metallicity and low gas content. In IC 10 we observe structures on a variety of size scales that all appear to be gravitationally bound. This effect may help explain the rather high star formation rate in IC 10.Comment: 20 pages with 6 ps figures, accepted for publication in The Astrophysical Journa

About the initial mass function and HeII emission in young starbursts

We demonstrate that it is crucial to account for the evolution of the starburst population in order to derive reliable numbers of O stars from integrated spectra for burst ages t > 2 - 3 Myr. In these cases the method of Vacca & Conti (1992) and Vacca (1994) systematically underestimates the number of O stars. Therefore the current WR/O number ratios in Wolf-Rayet (WR) galaxies are overestimated. This questions recent claims about flat IMF slopes (alpha ~ 1-2) in these objects. If the evolution of the burst is properly treated we find that the observations are indeed compatible with a Salpeter IMF, in agreement with earlier studies. Including recent predictions from non-LTE, line blanketed model atmospheres which account for stellar winds, we synthesize the nebular and WR HeII 4686 emission in young starbursts. For metallicities 1/5 <= Z/Z_sun <= 1 we predict a strong nebular HeII emission due to a significant fraction of WC stars in early WR phases of the burst. For other metallicities broad WR emission will always dominate the HeII emission. Our predictions of the nebular HeII intensity agree well with the observations in WR galaxies and an important fraction of the giant HII regions where nebular HeII is detected. We propose further observational tests of our result.Comment: ApJ Letters, accepted. 8 pages LaTeX including 3 PostScript figures, uses AASTeX and psfig macros. PostScript file also available at ftp://ftp.stsci.edu/outside-access/out.going/schaerer/imf.p

Convection-permitting fully coupled WRF-Hydro ensemble simulations in high mountain environment: impact of boundary layer- and lateral flow parameterizations on land–atmosphere interactions

Numerical climate models have been upgraded by the improved description of terrestrial hydrological processes across different scales. The goal of this study is to explore the role of terrestrial hydrological processes on land–atmosphere interactions within the context of modeling uncertainties related to model physics parameterization. The models applied are the Weather Research and Forecasting (WRF) model and its coupled hydrological modeling system WRF-Hydro, which depicts the lateral terrestrial hydrological processes and further allows their feedback to the atmosphere. We conducted convection-permitting simulations (3 km) over the Heihe River Basin in Northwest China for the period 2008–2010, and particularly focused on its upper reach area of complex high mountains. In order to account for the modeling uncertainties associated with model physics parameterization, an ensemble of simulations is generated by varying the planetary boundary layer (PBL) schemes. We embedded the fully three-dimensional atmospheric water tagging method in both WRF and WRF-Hydro for quantifying the strength of land–atmosphere interactions. The impact of PBL parameterization on land–atmosphere interactions is evaluated through its direct effect on vertical mixing. Results suggest that enabled lateral terrestrial flow in WRF-Hydro distinctly increases soil moisture and evapotranspiration near the surface in the high mountains, thereby modifies the atmospheric condition regardless of the applied PBL scheme. The local precipitation recycling ratio in the study area increases from 1.52 to 1.9% due to the description of lateral terrestrial flow, and such positive feedback processes are irrespective of the modeling variability caused by PBL parameterizations. This study highlights the non-negligible contribution of lateral terrestrial flow to local precipitation recycling, indicating the potential of the fully coupled modeling in land–atmosphere interactions research