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  • 1
    Electronic Resource
    Electronic Resource
    Influence of extracellular Cl concentration on Cl transport across isolated skin ofRana Pipiens (1980)
    Springer
    The journal of membrane biology 56 (1980), S. 81-92 
    Details
    ISSN: 1432-1424
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary The effect of changes in Cl concentration in the external and/or serosal bath on Cl transport across short-circuited frog skin was studied by measurements of transepithelial Cl influx (J 13 Cl ) and efflux (J 31 Cl ), short-circuit current, transepithelial potential, and conductance (G m).J 13 Cl as well asJ 31 Cl were found to have a saturating component and a component which is apparently linear with Cl concentration. The linear component ofJ 31 Cl appears only upon addition of Cl to external medium, and about 3/4 of this component does not contribute toG m. The saturating component ofJ 31 Cl is only 5% of totalJ 31 Cl with 115mm Cl in the serosal medium. Replacement of 115mm Cl− in external medium by SO 4 = , NO 3 − , HCO 3 − or I− results in 87–97% reduction ofJ 31 Cl , whereas replacement with Br− has no effect. As external Cl concentration is raised in steps from 2 to 115mm,J 13 Cl andJ 31 Cl increase by the same amount butJ 13 Cl is persistently 0.15 μeq/cm2 hr larger thanJ 31 Cl . These results indicate that at least 3/4 of linear components ofJ 13 Cl andJ 31 Cl proceed via an exchange diffusion mechanism which seems to be located at the outer cell border. The saturating component ofJ 13 Cl is involved in active Cl transport in an inward direction, and there is evidence suggesting that Cl uptake across outer cell border, which proceeds against an electrochemical gradient, is electroneutral but not directly linked to Na.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01869355
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  • 2
    Electronic Resource
    Electronic Resource
    Effect of external cation and anion substitutions on sodium transport in isolated frog skin (1980)
    Springer
    The journal of membrane biology 52 (1980), S. 121-132 
    Details
    ISSN: 1432-1424
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary Effects of changes in external ionic strength, external cation and/or anion substitution on transepithelial influx and efflux of sodium, short-circuit current and on transepithelial potential difference and resistance were studied in isolated frog skin. Active transport of Na was found to be highly dependent on both anionic and cationic composition of external medium. Relative abilities of external monovalent cations to inhibit active Na transport were H〉Li〉K〉Rb〉Cs〉choline. Relative abilities of external monovalent anions to stimulate active Na transport were I〉Br〉Cl. Sequences of anion interaction and of resistance changes suggest that anionic stimulation of Na transport is not due to electrical coupling across outer cell membrane. The ability of different anions and cations to alter Na transport suggests that externally located charged groups act as important barriers or filters to ion movement. In addition, the experiments suggest that an increase in ionic strength of external medium has an effect on active transport of Na, a finding that indicates interference of surface charges with Na entry. Directional changes in efflux of Na due to changes in ionic composition of external medium usually paralleled changes in active Na transport. It is possible that the observed relationship between influx and efflux of Na is the result of common pathways and of interaction of the active transport system with Na efflux.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01869117
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  • 3
    Electronic Resource
    Electronic Resource
    Effect of FeCl3 on ion transport in isolated frog skin (1980)
    Springer
    The journal of membrane biology 52 (1980), S. 133-139 
    Details
    ISSN: 1432-1424
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary The effect of addition of FeCl3 to the media bathing the isolated skin ofRana pipiens was studied by measuring short-circuit current, transepithelial potential, and resistance, and by determining the influx and efflux of sodium (J 13 Na andJ 31 Na , respectively) and the influx and efflux of chloride (J 13 Cl andJ 31 Cl , respectively) across the epithelium. With normal Ringer's solution on both sides of the skin, addition of 10−3 m FeCl3 to the external medium resulted in nearly complete inhibition of active Na transport (J 13 Na decreased from 1.30±0.14 to 0.10±0.04 μeq/cm2 hr (N=8)) and in appearance of active chloride transport in outward direction due to an 80% increase inJ 31 Cl . Average (J 31 Cl −J 13 Cl ) obtained from means of 8 skins in 6 consecutive control and last 3 experimental periods was −0.17±0.04 and 0.38±0.05 μeq/cm2 hr, respectively. FeCl3 added to external medium also induced substantial net chloride movement in outward direction when external medium contained Na-free choline chloride Ringer's or low ionic strength solution. Under the latter condition net Na movement was virtually eliminated by external FeCl3. After addition of FeCl3 to serosal medium there was delayed inhibition ofJ 13 Na but no change in chloride fluxes. Immediate and profound changes in Na and Cl transport systems seen after external application of FeCl3 indicate charge effects of Fe3+ on surface of apical cell membranes, possibly close to or in ion channels.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01869118
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  • 4
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    Predicting olivine composition using Raman spectroscopy through band shift and multivariate analyses (2018)
    Mineralogical Society of America
    Details
    Publication Date: 2018-01-01
    Description: Olivine group minerals are ubiquitous in extrusive igneous rocks and play an important role in constraining equilibria for samples in the upper mantle and above. All Raman spectra of the olivine group minerals in the solid solution between forsterite (Fo, Mg2SiO4) and fayalite (Fa, Fe2SiO4) have a high-intensity doublet between 800 and 880 cm–1. Previous studies used small sample suites with limited compositional ranges and varying spectrometers to relate energy shifts of these two bands to Mg/Fe contents. In this work, Raman spectra of 93 olivine samples were acquired on either Bruker's 532 nm (laser wavelength) Senterra or BRAVO (785/852.3 nm) spectrometer. This paper compares the two-peak band shift univariate method with two multivariate methods: partial least squares (PLS) and the least absolute shrinkage operator (Lasso). Data sets from several instruments are also examined to assess the most accurate method for predicting olivine composition from a Raman spectrum.Our 181-spectra PLS model is recommended for use when determining olivine composition from a Raman spectrum. For Raman spectra of mixed phases where only the olivine doublet can be identified, composition can best be determined using the position of the peak ca. 838–857 cm–1 through use of the regression equation %Fo = –0.179625x2 + 310.077x –133 717 (where x = DB2 centroid in units of cm–1).In situ methods for predicting mineral composition on planetary surfaces are critically important to extraterrestrial exploration going forward; of these, Raman spectroscopy is likely the best, as shown by the impending deployment of several Raman instruments to Mars (ExoMars and Mars 2020). More broadly, application of machine learning methods to spectral data processing have implications to multiple fields that use spectroscopic data.
    Print ISSN: 0003-004X
    Electronic ISSN: 1945-3027
    Topics: Geosciences
    Published by Mineralogical Society of America
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  • 5
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    Neural network radiative transfer for imaging spectroscopy (2019)
    Copernicus
    Details
    Publication Date: 2019-05-02
    Description: Visible–shortwave infrared imaging spectroscopy provides valuable remote measurements of Earth's surface and atmospheric properties. These measurements generally rely on inversions of computationally intensive radiative transfer models (RTMs). RTMs' computational expense makes them difficult to use with high-volume imaging spectrometers, and forces approximations such as lookup table interpolation and surface–atmosphere decoupling. These compromises limit the accuracy and flexibility of the remote retrieval; dramatic speed improvements in radiative transfer models could significantly improve the utility and interpretability of remote spectroscopy for Earth science. This study demonstrates that nonparametric function approximation with neural networks can replicate radiative transfer calculations and generate accurate radiance spectra at multiple wavelengths over a diverse range of surface and atmosphere state parameters. We also demonstrate such models can act as surrogate forward models for atmospheric correction procedures. Incorporating physical knowledge into the network structure provides improved interpretability and model efficiency. We evaluate the approach in atmospheric correction of data from the PRISM airborne imaging spectrometer, and demonstrate accurate emulation of radiative transfer calculations, which run several orders of magnitude faster than first-principles models. These results are particularly amenable to iterative spectrum fitting approaches, providing analytical benefits including statistically rigorous treatment of uncertainty and the potential to recover information on spectrally broad signals.
    Print ISSN: 1867-1381
    Electronic ISSN: 1867-8548
    Topics: Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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  • 6
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    Neural Network Radiative Transfer for Imaging Spectroscopy (2019)
    Copernicus
    Details
    Publication Date: 2019-01-18
    Description: Visible/Shortwave InfraRed imaging spectroscopy provides valuable remote measurements of Earth's surface and atmospheric properties. These measurements generally rely on inversions of computationally-intensive Radiative Transfer Models (RTMs). RTMs' computational expense makes them difficult to use with high volume imaging spectrometers, and forces approximations such as lookup table interpolation and surface/atmosphere decoupling. These compromises limit the accuracy and flexibility of the remote retrieval; dramatic speed improvements in radiative transfer models could significantly improve the utility and interpretability of remote spectroscopy for Earth science. This study demonstrates that nonparametric function approximation with neural networks can replicate Radiative Transfer calculations over a relevant range of surface/atmosphere parameters. Incorporating physical knowledge into the network structure provides improved interpretability and model efficiency. We evaluate the approach in atmospheric correction of data from the PRISM airborne imaging spectrometer, and demonstrate accurate emulation of radiative transfer calculations which run several orders of magnitude faster than first-principles models. These results are particularly amenable to iterative spectrum fitting approaches, providing analytical benefits including statistically rigorous treatment of uncertainty and the potential to recover information on spectrally-broad signals.
    Electronic ISSN: 1867-8610
    Topics: Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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  • 7
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    Effect of Li and of other ions on Na transport in epithelial cells of frog skin (1980)
    Elsevier
    Details
    Publication Date: 1980-08-01
    Print ISSN: 0006-2952
    Electronic ISSN: 1873-2968
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Published by Elsevier
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