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  • 1
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    HST hot-Jupiter transmission spectral survey: evidence for aerosols and lack of TiO in the atmosphere of WASP-12b (2013)
    Oxford University Press
    Details
    Publication Date: 2013-11-30
    Description: We present Hubble Space Telescope ( HST ) optical transmission spectra of the transiting hot-Jupiter WASP-12b, taken with the Space Telescope Imaging Spectrograph instrument. The resulting spectra cover the range 2900–10 300 Swhich we combined with archival Wide Field Camera 3 spectra and Spitzer photometry to cover the full optical to infrared wavelength regions. With high spatial resolution, we are able to resolve WASP-12A's stellar companion in both our images and spectra, revealing that the companion is in fact a close binary M0V pair, with the three stars forming a triple-star configuration. We derive refined physical parameters of the WASP-12 system, including the orbital ephemeris, finding the exoplanet's density is ~20 per cent lower than previously estimated. From the transmission spectra, we are able to decisively rule out prominent absorption by TiO in the exoplanet's atmosphere, as there are no signs of the molecule's characteristic broad features nor individual bandheads. Strong pressure-broadened Na and K absorption signatures are also excluded, as are significant metal-hydride features. We compare our combined broad-band spectrum to a wide variety of existing aerosol-free atmospheric models, though none are satisfactory fits. However, we do find that the full transmission spectrum can be described by models which include significant opacity from aerosols: including Rayleigh scattering, Mie scattering, tholin haze and settling dust profiles. The transmission spectrum follows an effective extinction cross-section with a power law of index α, with the slope of the transmission spectrum constraining the quantity α T  = –3528 ± 660 K, where T is the atmospheric temperature. Rayleigh scattering (α = –4) is among the best-fitting models, though requires low terminator temperatures near 900 K. Sub-micron size aerosol particles can provide equally good fits to the entire transmission spectrum for a wide range of temperatures, and we explore corundum as a plausible dust aerosol. The presence of atmospheric aerosols also helps to explain the modestly bright albedo implied by Spitzer observations, as well as the near blackbody nature of the emission spectrum. Ti-bearing condensates on the cooler night-side is the most natural explanation for the overall lack of TiO signatures in WASP-12b, indicating the day/night cold trap is an important effect for very hot Jupiters. These findings indicate that aerosols can play a significant atmospheric role for the entire wide range of hot-Jupiter atmospheres, potentially affecting their overall spectrum and energy balance.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 2
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    Changes in expression profiles of genes associated with DNA repair following induction of DNA damage in larval zebrafish Danio rerio (2013)
    Oxford University Press
    Details
    Publication Date: 2013-08-15
    Description: DNA repair is initiated by transcription of genes in response to specific types of damage. Breaks in DNA strands (single and double) are repaired predominantly through non-homologous end-joining (NHEJ) or homologous recombination (HR), but progression of repair and changes in expression profiles of genes involved are unknown. DNA damage was induced in zebrafish larvae by brief exposure (10min) to hydrogen peroxide (H 2 O 2 ; 100mM), and induction of DNA strand breaks was assessed by single-cell gel electrophoresis (comet) assay over 24h. H 2 O 2 was selected because it is eliminated rapidly after induction of DNA damage. DNA damage [mean ± standard error of the mean (SEM), % tail DNA] increased significantly immediately after 10-min H 2 O 2 exposure (35.4±3.8; control 17.2±2.0), but damage did not differ from control levels 24h after exposure (9.2±0.4; control 9.9±0.9). At 0-, 1-, 3-, 6-, 12- and 24-h post-exposure, quantitative reverse transcriptase–PCR was conducted to assess expression of selected genes involved in DNA repair including xrcc5 , xrcc6 (NHEJ), rad51 (HR) and gadd45a (DNA damage detection). Expression (maximum fold-change ± SEM, triplicate samples of 40 larvae) of each gene increased rapidly (within 6h) after exposure to 100mM of H 2 O 2 : 1.8±0.2, rad51 ; 1.7±0.2, xrcc5 and 1.5±0.1, xrcc6. Acute exposure (200mM of H 2 O 2 ) caused 10% larval mortality within 2h, upregulated gadd45a (5.0±0.8), but did not change expression of rad51, xrcc5 or xrcc6 . Expression profiles (critical exponential model) were similar among genes but differed relative to time and among independent experiments. Results indicate that repair mechanisms are initiated rapidly after DNA damage, that gene expression profiles vary according to potency of H 2 O 2 exposure and that examination of the time course of gene expression changes is necessary to understand the complete gene response over time.
    Print ISSN: 0267-8357
    Electronic ISSN: 1464-3804
    Topics: Biology , Medicine
    Published by Oxford University Press
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  • 3
    Electronic Resource
    Electronic Resource
    Analysis of three- and four-compartment models forin vivo radioligand-neuroreceptor interaction (1987)
    Springer
    Bulletin of mathematical biology 49 (1987), S. 469-486 
    Details
    ISSN: 1522-9602
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract Currently applied three-copartment models for analyzing kinetic data derived fromin vivo positron emission tomographic (PET) studies of radioligand-neuroreceptor interactions require assumptions which may not be strictly valid. Such assumptions include very rapid kinetics for nonspecific binding and the absence of multiple specific receptors or subtypes. Computer simulations, based on an exact analytical solution of the relevant differential equations, indicate the numerical errors that can arise when the assumptions are invalid. We propose a fourcompartment model which requires fewer assumptions. A simple relationship is derived for expressing the microscopic rate constants of either the three- or four-compartment model as explicit functions of the experimentally-observed macroscopic rate constants. This could eliminate the need for time-consuming, iterative, non-linear, curve-fitting approaches and numerical integration. The usefulness of the four-compartment model is limited, however, by the sensitivity and temporal resolution of current PET imaging devices.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02458864
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  • 4
    Electronic Resource
    Electronic Resource
    Structural studies of some derivatives of cis, cis-cyclohexane-1,3,5-tricarboxylic acid (1991)
    Springer
    Journal of chemical crystallography 21 (1991), S. 297-308 
    Details
    ISSN: 1572-8854
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract cis,cis-Cyclohexane-1,3,5-tricarboxylic acid (1) its trimethyl ester (2) and their 1,3,5-trimethylated and 1,3,5-tribenzylated derivatives were prepared, and their structures studied by two-dimensional NMR spectroscopy in conjunction with X-ray crystallography. The results show that these molecules adopt a chair conformation in solution, with all the carboxyl groups in1 and all the methoxycarbonyl groups in2 occupying the equatorial positions, but with the corresponding functionalities in the alkylated derivatives occupying the axial positions. For2, its 1,3,5-tribenzylated derivative4, andcis,cis-1,3,5-trimethylcyclohexane-1,3,5-tricarboxylic acid (5), the same conformational preferences are seen to persist in the crystalline state as in solution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01156081
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  • 5
    Electronic Resource
    Electronic Resource
    Synthesis and structural characterization of 5,6,15,16-tetradehydrobenzo[a]phenanthro[9, 10-e]cyclooctene, C24H12 (1996)
    Springer
    Journal of chemical crystallography 26 (1996), S. 227-230 
    Details
    ISSN: 1572-8854
    Keywords: 5,6,15,16-Tetradehydrobenzo[a]phenanthro[9, 10-e]cyclooctene ; planar dehydro[8]annulenes ; angle-strained alkynes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract A benzo-phenanthro-fused planar cyclooctatetraene derivative, namely, 5,6,15,16-tetradehydrobenzo[a]phenanthro[9, 10-e]cyclooctene (5) was synthesized in two steps from the known benzo[a]phenanthro[9, 10-e]cyclooctene (6). Compound5 crystallizes in space groupPbam witha=9.828(2),b=19.466(4),c=15.901(3) Å, and Z=8. X-Ray analysis (MoKα radiation,R=0.060 for 1233 observed data) has shown that both independent molecules have the same planarC 2v configuration with averaged bond lengths of 1.381(7) and 1.208(7) Å for the phenanthrene C6a−C14b bond and the acetylenic C≡C bond, respectively.1H and13C NMR spectral results of 5 and 5,6,15,16-tetrabromo-5,6,15,16-tetrahydrobenzo[a]phenanthro[9, 10-e]cyclooctene (7) are also presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01673676
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  • 6
    Electronic Resource
    Electronic Resource
    Reaction of 2-methylnaphthalene with hexachlorocyclopentadiene and structural characterization of a new addition-substitution product (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 787-790 
    Details
    ISSN: 1572-8854
    Keywords: 2-Methylnaphthalene ; hexachlorocyclopentadiene ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract 2-Methylnaphthalene undergoes Diels-Alder addition and substitution with hexachlorocyclopentadiene to give two products, 1,2,3,4,5,6,7,8,13,13,14,14-dodecachloro-1,4,4a,4b,5,8,8a,12b-octahydro-10-methyl-1,4;5,8-dimethanotriphenylene 1 and 1,2,3,4,5,6,7,8,13,13,14,14-dodecachloro-1,4,4a,4b,5,8,8a,12b-octahydro-10-(1′,2′,3′,4′,5′-pentachlorocyclopentadienyl)methyl-1,4;5,8-dimethanotriphenylene 2. The molecular structure of 2 has been characterized by X-ray crystallography: C26H9Cl17, monoclinic, space group P21/c, with a = 15.316(3), b = 13.698(3), c = 16.116(3) Å, β = 96.113(3)°, and Z = 4.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1021819518557
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  • 7
    Electronic Resource
    Electronic Resource
    Inference of ground surface temperature history from subsurface temperature data: Interpreting ensembles of borehole logs (1996)
    Springer
    Pure and applied geophysics 147 (1996), S. 537-550 
    Details
    ISSN: 1420-9136
    Keywords: Borehole temperature ; climate change ; inversion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Ground surface temperature histories (GSTHs) inferred from borehole temperaturedepth (T-z) data are often degraded, to a various extent, by random or systematic noise in theT-z data and in the measurements of thermophysical properties of the earth. To minimize the effects of noise, and hence improve the fidelity of the inferred GSTH, a plausible approach is to perform a simultaneous inversion, of theT-z logs in a region, or alternatively, to invert the individualT-z logs and then average the resulting GSTHs. Averaging and simultaneous inversion are conceptually different: whereas an averaging can always be peformed, a simultaneous inversion is predicated on the assumption of a common transient component of the GSTH in all theT-z logs. In this work we examine and compare the two approaches, using a time domain inverse formulation based on the method of least squares. We consider a set of scenarios: (a) multipleT-z logs from a single borehole, (b) multiple boreholes from a single site, (c) multiple boreholes in similar climatological settings, and (d) multiple boreholes in different climatological settings. We show that for (a), (b) and (c), averaging and simultaneous inversion yield nearly identical results. For boreholes in different settings, the assumption of a common transient GSTH may be invalid and averaging and simultaneous inversion give divergent results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00878843
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  • 8
    Electronic Resource
    Electronic Resource
    Determination of optimum minimum flow from a dam by using energy analysis (1984)
    Springer
    Environmental management 8 (1984), S. 345-352 
    Details
    ISSN: 1432-1009
    Keywords: Energy analysis ; Dams ; Hydroelectric projects ; Environmental assessment ; Trade-offs ; Environmental planning
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The proposed restoration of an abandoned hydroelectric dam on the Quinebaug River, Connecticut, is studied using energy analysis. The analysis considers the effects of alternative minimum flow releases, ranging from 0 to 34 cubic meters per second (cms), on the total energy flow of the affected system. The principal system components affected by differing minimum flows are hydroelectric power generation, aquatic habitat, and gross aquatic ecosystem productivity. The minimum flow alternative resulting in the highest annual energy flow in the affected system is considered optimal. From this purely analytical point of view, the optimum minimum flow is 0 cms, due to the short length and low productivity of the regulated reach, and the lack of floodplain interactions. Simulations of longer and more productive river reaches were conducted. For very short, unproductive reaches, in the absence of a floodplain, the contribution of aquatic community productivity to total system energy flow is negligible compared to hydroelectric generation. Optimum minimum flows are higher for longer and more productive reaches. For such cases the operation of hydroelectric dams could reduce total system energy flow because the energy supplied by hydroelectric generation may be offset by losses in aquatic productivity due to diminished riverine habitat.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01868033
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  • 9
    Electronic Resource
    Electronic Resource
    Altered aggregational properties in a genetic variant of human glucose 6-phosphate dehydrogenase (1969)
    Springer
    Biochemical genetics 3 (1969), S. 137-150 
    Details
    ISSN: 1573-4927
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The Tel Hashomer variant of human G6PD migrates as two prominent components during electrophoresis in several gel systems in which red cell G6PD from other males migrates predominantly as a single band. Since human males normally have but one X-chromosome, the extra band of this variant seemed an exception to earlier biochemical and genetic observations suggesting that human red cell G6PD is determined by a locus on the X chromosome. Results of the present studies indicate that the Tel Hashomer variant is unusually susceptible to the formation of a complex which has a higher molecular weight than normal G6PD and which represents the slow electrophoretic component. The conditions of formation and disruption of this complex in crude and purified Tel Hashomer preparations suggest that it results from the formation of disulfide bridges between molecules of Tel Hashomer G6PD.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00520349
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  • 10
    Electronic Resource
    Electronic Resource
    Mast cell immunohistochemistry: non-immunological immunostaining mediated by non-specific F(ab′)2-mast cell secretory granule interaction (1993)
    Springer
    Journal of molecular histology 25 (1993), S. 642-647 
    Details
    ISSN: 1573-6865
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary During investigations of murine and human mast cell immunoreactivity with potential anti-interleukin-4 antibodies, non-specific, non-immunological labelling of mouse and human mast cells became apparent. Non-specific, non-immunological labelling was identified by (i) immunolabelling of mast cells when using control isotype primary antibodies, (ii) ability of conjugated secondary antibodies to label mast cells without prior mast cell exposure to a primary antibody, (iii) extinction of the non-specific labelling and retention of specific labelling when the pH of the diluting and washing buffers is shifted from pH 7.2 to pH 6.0, and (iv) reduction/extinction of the labelling when the antibodies are pre-incubated with soluble heparin prior to immunostaining. The site of the reactivity on the electron microscope level was shown to be confined to the mast cell secretory granules. The results of this study support the hypothesis that non-specific labelling of mast cells results from an ionic interaction between the F(ab′)2 segments of antibodies and the heparin constituent of the mast cell secretory granules. This study points out the necessity of stringent controls when using immunohistochemistry to determine mast cell reactivity to various antibodies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00157878
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