Hydration Status Response to Bolus Frequency and Volume Intake During Exercise in Heat

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Adoption of Conservation-Tillage Practices in Cotton Production

Replaced with revised version of paper 10/23/07.conservation tillage, cotton, genetically modified seed, herbicide-resistant cotton, stacked-gene cotton, simultaneous logit model, single-equation logit model, technology adoption, Crop Production/Industries,

Spatial epidemiological patterns suggest mechanisms of land-sea transmission for Sarcocystis neurona in a coastal marine mammal.

Sarcocystis neurona was recognised as an important cause of mortality in southern sea otters (Enhydra lutris nereis) after an outbreak in April 2004 and has since been detected in many marine mammal species in the Northeast Pacific Ocean. Risk of S. neurona exposure in sea otters is associated with consumption of clams and soft-sediment prey and is temporally associated with runoff events. We examined the spatial distribution of S. neurona exposure risk based on serum antibody testing and assessed risk factors for exposure in animals from California, Washington, British Columbia and Alaska. Significant spatial clustering of seropositive animals was observed in California and Washington, compared with British Columbia and Alaska. Adult males were at greatest risk for exposure to S. neurona, and there were strong associations with terrestrial features (wetlands, cropland, high human housing-unit density). In California, habitats containing soft sediment exhibited greater risk than hard substrate or kelp beds. Consuming a diet rich in clams was also associated with increased exposure risk. These findings suggest a transmission pathway analogous to that described for Toxoplasma gondii, with infectious stages traveling in freshwater runoff and being concentrated in particular locations by marine habitat features, ocean physical processes, and invertebrate bioconcentration

Hybridization Mechanism for Cohesion of Cd-based Quasicrystals

Cohesion mechanism of cubic approximant crystals of newly discovered binary quasicrystals, Cd$_6$M (M=Yb and Ca), are studied theoretically. It is found that stabilization due to alloying is obtained if M is an element with low-lying unoccupied $d$ states. This leads to conclusion that the cohesion of the Cd-based compounds is due to the hybridization of the $d$ states of Yb and Ca with a wide $sp$ band. %unlike known stable quasicrystals without transition elements %such as Al-Li-Cu and Zn-Mg-RE (RE:rare earth). Although a diameter of the Fermi sphere coincides with the strong Bragg peaks for Cd-Yb and Cd-Ca, the Hume-Rothery mechanism does not play a principal role in the stability because neither distinct pseudogap nor stabilization due to alloying is obtained for isostructural Cd-Mg. In addition to the electronic origin, matching of the atomic size is very crucial for the quasicrystal formation of the Cd-based compounds. It is suggested that the glue atoms, which do not participate in the icosahedral cluster, play an important role in stabilization of the compound.Comment: 4 pages, 2 figure

Testing the locality of transport in self-gravitating accretion discs - II. The massive disc case

In this paper, we extend our previous analysis (Lodato & Rice 2004) of the transport properties induced by gravitational instabilities in cooling, gaseous accretion discs to the case where the disc mass is comparable to the central object. In order to do so, we have performed global, three-dimensional smoothed particle hydrodynamics simulations of massive discs. These new simulations show a much more complex temporal evolution with respect to the less massive case. Whereas in the low disc mass case a self-regulated, marginally stable state (characterized by an approximately constant radial profile of the stability parameter $Q$) is easily established, in the high disc mass case we observe the development of an initial transient and subsequent settling down in a self-regulated state in some simulations, or a series or recurrent spiral episodes, with low azimuthal wave number $m$, in others. Accretion in this last case can therefore be a highly variable process. On the other hand, we find that the secular evolution of the disc is relatively slow. In fact, the time-average of the stress induced by self-gravity results in accretion time-scales much longer than the dynamical timescale, in contrast with previous isothermal simulations of massive accretion discs. We have also compared the resulting stress tensor with the expectations based on a local theory of transport, finding no significant evidence for global wave energy transport.Comment: MNRAS, accepted (higher quality, colour figures can be found at http://www.ast.cam.ac.uk/~giuseppe/Publications/Locality_II/

A multi-wavelength census of stellar contents in the young cluster NGC 1624

We present a comprehensive multi-wavelength analysis of the young cluster NGC 1624 associated with the H II region Sh2-212 using optical UBVRI photometry, optical spectroscopy and GMRT radio continuum mapping along with the near-infrared (NIR) JHK archival data. Reddening E(B-V) and distance to the cluster are estimated to be 0.76 - 1.00 mag and 6.0 +/- 0.8 kpc, respectively. Present analysis yields a spectral class of O6.5V for the main ionizing source of the region. The distribution of YSOs in (J-H)/ (H-K) NIR colour-colour diagram shows that a majority of them have A_V $\le$ 4 mag. Based on the NIR excess characteristics, we identified 120 probable candidate YSOs in this region which yield a disk frequency of ~ 20%. These YSOs are found to have an age spread of ~ 5 Myr with a median age of ~ 2-3 Myr and a mass range of ~ 0.1 - 3.0 $M_\odot$. A significant number of YSOs are located close to the cluster centre and we detect an enhanced density of reddened YSOs located/projected close to the molecular clumps at the periphery of NGC 1624. This indicates that the YSOs located within the cluster core are relatively older in comparison to those located/projected near the clumps. From the radio continuum flux, spectral class of the ionizing source of the ultra-compact H II region at the periphery of Sh2-212 is estimated to be ~ B0.5V. From optical data, slope of the mass function (MF) $\Gamma$, in the mass range $1.2 \le M/M_{\odot}<27$ can be represented by a single power law with a slope -1.18 +/- 0.10, whereas the NIR data in the mass range $0.65 \le M/M_{\odot}<27$ yields $\Gamma$ = -1.31 +/- 0.15. The slope of the K-band luminosity function (KLF) for the cluster is found to be 0.30 +/- 0.06 which is in agreement with the values obtained for other young clusters.Comment: Accepted for publication in MNRA

Atomic Fluorine Beam Etching Of Silicon And Related Materials

A 1 eV neutral atomic fluorine beam has been shown to produce etch rates in silicon as high as 1 µm/min. Using a CaF 2 resist layer we fabricated 120 µm-deep by 1 µm-wide trenches (aspect ratio 120:1) in silicon with little sidewall taper (slopes of about 1000:1) or aspect-ratio dependent etching effects. Achieving such anisotropic etching suggests that the scattered species do not contribute significantly to sidewall etching under the conditions of this experiment. We estimate that the ultimate depth attainable for a 1 µm-wide trench is about 250 µm and that the critical parameter for attaining a trench of a certain depth is the aspect ratio. Our observations and analysis suggest that this etching technique can be used to fabricate trenches on a nanoscale level while maintaining high aspect ratios of 100 or greater. JVST_web.doc 09/12/99

The GALEX Arecibo SDSS Survey II: The Star Formation Efficiency of Massive Galaxies

We use measurements of the HI content, stellar mass and star formation rates in ~190 massive galaxies with stellar masses greater than 10^10 Msun, obtained from the Galex Arecibo SDSS Survey (GASS) described in Paper I (Catinella et al. 2010) to explore the global scaling relations associated with the bin-averaged ratio of the star formation rate over the HI mass, which we call the HI-based star formation efficiency (SFE). Unlike the mean specific star formation rate, which decreases with stellar mass and stellar mass surface density, the star formation efficiency remains relatively constant across the sample with a value close to SFE = 10^-9.5 yr^-1 (or an equivalent gas consumption timescale of ~3 Gyr). Specifically, we find little variation in SFE with stellar mass, stellar mass surface density, NUV-r color and concentration. We interpret these results as an indication that external processes or feedback mechanisms that control the gas supply are important for regulating star formation in massive galaxies. An investigation into the detailed distribution of SFEs reveals that approximately 5% of the sample shows high efficiencies with SFE > 10^-9 yr^-1, and we suggest that this is very likely due to a deficiency of cold gas rather than an excess star formation rate. Conversely, we also find a similar fraction of galaxies that appear to be gas-rich for their given specific star-formation rate, although these galaxies show both a higher than average gas fraction and lower than average specific star formation rate. Both of these populations are plausible candidates for "transition" galaxies, showing potential for a change (either decrease or increase) in their specific star formation rate in the near future. We also find that 36+/-5% of the total HI mass density and 47+/-5% of the total SFR density is found in galaxies with stellar mass greater than 10^10 Msun. [abridged]Comment: 18 pages, 11 figures. Accepted for publication in MNRAS. GASS publications and released data can be found at http://www.mpa-garching.mpg.de/GASS/index.ph