Bulk crystal growth and surface preparation of NiSb, MnSb, and NiMnSb

Bulk single crystal and polycrystalline samples of NiSb, MnSb, and NiMnSb have been grown and characterized. The lattice parameter of NiMnSb was found to be 5.945 ± 0.001 Å, around 0.25% larger than previous reports. The surface preparation of these materials was investigated using x-ray photoelectron spectroscopy. Wet etching with HCl and argon ion sputtering were used in tandem with vacuum annealing. For both binary materials, a clean and stoichiometric surface could be regained by HCl etching and annealing alone. However, clean and stoichiometric ternary NiMnSb was not successfully prepared by these methods. The transition metal 2p and 3p levels are analyzed for all three materials

Spatial distribution of fibropapillomatosis in green turtles along the Queensland coast and an investigation into the influence of water quality on prevalence

Fibropapillomatosis (FP) is a tumor-forming disease which affects all species of marine turtle, but predominantly the green turtle (Chelonia mydas). Expression of this disease is thought to be precipitated by poor environmental conditions and often linked to anthropogenically induced environmental changes. Although FP is a globally distributed disease, targeted studies on the spatial distribution of the disease in Australia are limited. Here, we present the first comprehensive report of FP prevalence in Queensland, Australia. A retrospective analysis of 25,645 capture records for 15 sites along the Queensland coast were used to determine FP prevalence and trends in foraging green turtles. Within this data set, 791 turtles (3.1%) with FP tumors were recorded. Our analysis showed that prevalence varies between sites and years, with juvenile turtles being the most frequently affected by the disease. We found that survey method has a significant influence on the apparent FP prevalence detected at each site. That is, surveys which were explicitly FP-targeted detected higher numbers of individual turtles with FP, and therefore generated higher prevalence rates than comprehensive population surveys. We also report the first attempt at developing water quality indices (WQIs) to compare with FP prevalence data in foraging green turtles. The WQIs were built from metrics published in a range of peer-reviewed papers, reports, and based on expert opinion. Despite utilizing an extensive data set, a relationship between FP prevalence and WQI rankings at each site could not be quantified. The analysis was confounded by a range of limitations, including data gaps, varying temporal scales and data capture methods in the FP prevalence, and water quality data sets. This study has significant implications for management as it highlights the benefits of designing and collecting centralized data that can be integrated and used across multiple projects or programs

The Very Low Albedo of WASP-12b From Spectral Eclipse Observations with Hubble\textit{Hubble}

We present an optical eclipse observation of the hot Jupiter WASP-12b using the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope. These spectra allow us to place an upper limit of $A_g < 0.064$ (97.5% confidence level) on the planet's white light geometric albedo across 290--570 nm. Using six wavelength bins across the same wavelength range also produces stringent limits on the geometric albedo for all bins. However, our uncertainties in eclipse depth are $\sim$40% greater than the Poisson limit and may be limited by the intrinsic variability of the Sun-like host star --- the solar luminosity is known to vary at the $10^{-4}$ level on a timescale of minutes. We use our eclipse depth limits to test two previously suggested atmospheric models for this planet: Mie scattering from an aluminum-oxide haze or cloud-free Rayleigh scattering. Our stringent nondetection rules out both models and is consistent with thermal emission plus weak Rayleigh scattering from atomic hydrogen and helium. Our results are in stark contrast with those for the much cooler HD 189733b, the only other hot Jupiter with spectrally resolved reflected light observations; those data showed an increase in albedo with decreasing wavelength. The fact that the first two exoplanets with optical albedo spectra exhibit significant differences demonstrates the importance of spectrally resolved reflected light observations and highlights the great diversity among hot Jupiters.Comment: 8 pages, 4 figures, 1 table, published in ApJL, in pres

The Faint End of the Luminosity Function and Low Surface Brightness Galaxies

SHELS (Smithsonian Hectospec Lensing Survey) is a dense redshift survey covering a 4 square degree region to a limiting R = 20.6. In the construction of the galaxy catalog and in the acquisition of spectroscopic targets, we paid careful attention to the survey completeness for lower surface brightness dwarf galaxies. Thus, although the survey covers a small area, it is a robust basis for computation of the slope of the faint end of the galaxy luminosity function to a limiting M_R = -13.3 + 5logh. We calculate the faint end slope in the R-band for the subset of SHELS galaxies with redshif ts in the range 0.02 <= z < 0.1, SHELS_{0.1}. This sample contains 532 galaxies with R< 20.6 and with a median surface brightness within the half light radius of SB_{50,R} = 21.82 mag arcsec^{-2}. We used this sample to make one of the few direct measurements of the dependence of the faint end of the galaxy luminosity function on surface brightness. For the sample as a whole the faint end slope, alpha = -1.31 +/- 0.04, is consistent with both the Blanton et al. (2005b) analysis of the SDSS and the Liu et al. (2008) analysis of the COSMOS field. This consistency is impressive given the very different approaches of th ese three surveys. A magnitude limited sample of 135 galaxies with optical spectroscopic reds hifts with mean half-light surface brightness, SB_{50,R} >= 22.5 mag arcsec^{-2} is unique to SHELS_{0.1}. The faint end slope is alpha_{22.5} = -1.52+/- 0.16. SHELS_{0.1} shows that lower surface brightness objects dominate the faint end slope of the l uminosity function in the field, underscoring the importance of surface brightness limits in evaluating measurements of the faint end slope and its evolution.Comment: 34 pages, 13 figures, 3 tables, Astronomical Journal, in press (updated based on review

Transition-state vibrational analysis and isotope effects for COMT-catalyzed methyl transfer

Isotopic partition-function ratios (IPFRs) computed for transition structures (TSs) of the methyl-transfer reaction catalyzed by catechol O-methyltransferase and modeled by hybrid QM/MM methods are analyzed. The ability of smaller Hessians to reproduce trends in α-3H3 and 14Cα IPFRs as obtained using the much larger subset QM/MM Hessians from which they are extracted is investigated critically. A 6-atom-extracted Hessian reproduces perfectly the α-T3 IPFR values from the full-subset Hessians of all the TSs but not the α-14CIPFRs. Average AM1/OPLS-AA harmonic frequencies and mean-square amplitudes are presented for the 12 normal modes of the α-CH3 moiety within the active site of several enzymic transition structures, together with QM/MM potential energy scans along each of these modes to assess the degree of anharmonicity. A novel investigation of ponderal effects upon IPFRs suggests that the value for α-14C tends toward a limiting minimum whereas that for α-T3 tends toward a limiting maximum as the mass of the rest of the system increases. The transition vector is dominated by motions of atoms within the donor and acceptor moieties and is very well described as a simple combination of Walden-inversion “umbrella” bending and asymmetric stretching of the SCα and CαO bonds. The contribution of atoms of the protein residues Met40, Tyr68, and Asp141 to the transition vector is extremely small. Average valence force constants for the COMT TS show significant differences from early BEBOVIB estimates which were used in support of the compression hypothesis for catalysis. There is no correlation between TS IPFRs and the nonbonded distances for close contacts between the S atom of SAM and Tyr68 or between any of the H atoms of the transferring methyl group and either Met40 or Asp141

Source apportionment of PM2.5 in Cork Harbour, Ireland using a combination of single particle mass spectrometry and quantitative semi-continuous measurements

An aerosol time-of-flight mass spectrometer (ATOFMS) was deployed for the measurement of the size resolved chemical composition of single particles at a site in Cork Harbour, Ireland for three weeks in August 2008. The ATOFMS was co-located with a suite of semi-continuous instrumentation for the measurement of particle number, elemental carbon (EC), organic carbon (OC), sulfate and particulate matter smaller than 2.5 μm in diameter (PM2.5). The temporality of the ambient ATOFMS particle classes was subsequently used in conjunction with the semi-continuous measurements to apportion PM2.5 mass using positive matrix factorisation. The synergy of the single particle classification procedure and positive matrix factorisation allowed for the identification of six factors, corresponding to vehicular traffic, marine, long-range transport, various combustion, domestic solid fuel combustion and shipping traffic with estimated contributions to the measured PM2.5 mass of 23%, 14%, 13%, 11%, 5% and 1.5% respectively. Shipping traffic was found to contribute 18% of the measured particle number (20–600 nm mobility diameter), and thus may have important implications for human health considering the size and composition of ship exhaust particles. The positive matrix factorisation procedure enabled a more refined interpretation of the single particle results by providing source contributions to PM2.5 mass, while the single particle data enabled the identification of additional factors not possible with typical semi-continuous measurements, including local shipping traffic

Perils of Diagnosis and Detection of Subungual Squamous Cell Carcinoma

Subungual squamous cell carcinoma often presents with atypical clinical manifestations, which can lead to delays in diagnosis. The presence of a tumor can be masked by the presence of infections or other misleading pathological conditions. The authors report on techniques for adequate biopsy and excision of such tumors. A case of subungual squamous cell carcinoma with invasion into the underlying bone is presented. Clinical histopathological evidence is reviewed along with human papillomavirus typing. Accurate diagnosis requires a high index of suspicion and appropriate tissue sampling