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  • 1
    Electronic Resource
    Electronic Resource
    Quantitative structure-activity relationships by neural networks and inductive logic programming. II. The inhibition of dihydrofolate reductase by triazines (1994)
    Springer
    Journal of computer aided molecular design 8 (1994), S. 421-432 
    Details
    ISSN: 1573-4951
    Keywords: QSAR ; Artificial intelligence ; Neural networks ; DHFR inhibitors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary One of the largest available data sets for developing a quantitative structure-activity relationship (QSAR) — the inhibition of dihydrofolate reductase (DHFR) by 2,4-diamino-6,6-dimethyl-5-phenyl-dihydrotriazine derivatives — has been used for a sixfold cross-validation trial of neural networks, inductive logic programming (ILP) and linear regression. No statistically significant difference was found between the predictive capabilities of the methods. However, the representation of molecules by attributes, which is integral to the ILP approach, provides understandable rules about drug-receptor interactions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00125376
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Quantitative structure-activity relationships by neural networks and inductive logic programming. I. The inhibition of dihydrofolate reductase by pyrimidines (1994)
    Springer
    Journal of computer aided molecular design 8 (1994), S. 405-420 
    Details
    ISSN: 1573-4951
    Keywords: QSAR ; Artificial intelligence ; Neural networks ; DHFR inhibitors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Neural networks and inductive logic programming (ILP) have been compared to linear regression for modelling the QSAR of the inhibition of E. coli dihydrofolate reductase (DHFR) by 2,4-diamino-5-(substitured benzyl)pyrimidines, and, in the subsequent paper [Hirst, J.D., King, R.D. and Sternberg, M.J.E., J. Comput.-Aided Mol. Design, 8 (1994) 421], the inhibition of rodent DHFR by 2,4-diamino-6,6-dimethyl-5-phenyl-dihydrotriazines. Cross-validation trials provide a statistically rigorous assessment of the predictive capabilities of the methods, with training and testing data selected randomly and all the methods developed using identical training data. For the ILP analysis, molecules are represented by attributes other than Hansch parameters. Neural networks and ILP perform better than linear regression using the attribute representation, but the difference is not statistically significant. The major benefit from the ILP analysis is the formulation of understandable rules relating the activity of the inhibitors to their chemical structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00125375
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  • 3
    Electronic Resource
    Electronic Resource
    Feature construction with Inductive Logic Programming: A Study of Quantitative Predictions of Biological Activity Aided by Structural Attributes (1999)
    Springer
    Data mining and knowledge discovery 3 (1999), S. 37-57 
    Details
    ISSN: 1573-756X
    Keywords: constructive induction ; indicator variables ; ILP ; QSAR ; drug design ; scientific discovery
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract Recently, computer programs developed within the field of Inductive Logic Programming (ILP) have received some attention for their ability to construct restricted first-order logic solutions using problem-specific background knowledge. Prominent applications of such programs have been concerned with determining “structure-activity” relationships in the areas of molecular biology and chemistry. Typically the task here is to predict the “activity” of a compound (for example, toxicity), from its chemical structure. A summary of the research in the area is: (a) ILP programs have largely been restricted to qualitative predictions of activity (“high”, “low” etc.); (b) When appropriate attributes are available, ILP programs have equivalent predictivity to standard quantitative analysis techniques like linear regression. However ILP programs usually perform better when such attributes are unavailable; and (c) By using structural information as background knowledge, an ILP program can provide comprehensible explanations for biological activity. This paper examines the use of ILP programs as a method of “discovering” new attributes. These attributes could then be used by methods like linear regression, thus allowing for quantitative predictions while retaining the ability to use structural information as background knowledge. Using structure-activity tasks as a test-bed, the utility of ILP programs in constructing new features was evaluated by examining the prediction of biological activity using linear regression, with and without the aid of ILP learnt logical attributes. In three out of the five data sets examined the addition of ILP attributes produced statistically better results. In addition six important structural features that have escaped the attention of the expert chemists were discovered. The method used here to construct new attributes is not specific to the problem of predicting biological activity, and the results obtained suggest a wider role for ILP programs in aiding the process of scientific discovery.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009815821645
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  • 4
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    Synthetic aperture radar imaging of ocean waves - Comparison with wave measurements (1980)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: Synthetic aperture radar images of ocean waves were obtained in conjunction with reference wave data near Marineland, Florida, December 14, 1975. Each of the various types of measurements were processed into a form that allowed direct comparisons with the others. Maxima of radar spectra occurred at the same frequencies as the maxima of reference wave height spectra. In a comparison of a radar spectrum with observed spectra of wave height, wave orbital velocity, and surface slope the high-frequency portion of the radar spectrum lay near and between the wave height and the orbital velocity spectra but differed significantly from the surface slope spectrum. The radar-derived mean directions and model-fitted directional spreads of wave energy were close to the values from a directional wave buoy and indicated the accuracy of radar measurements of wave direction. However, a directional plot of a radar spectrum near shore at the frequency of the maximum showed a sharper peak than such a plot of a fitted spectrum derived from reference data.
    Keywords: OCEANOGRAPHY
    Type: Journal of Geophysical Research; 85; Sept. 20
    Format: text
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  • 5
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    Comparison of in situ and remotely sensed ocean waves off Marineland, Florida (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Comparison between X-band and L-band radar imagery of sea waves is made. Sea truth was obtained by in situ pitch-and-roll buoy measurements. Under the low wind and wave conditions of the tests, superior wave imagery and more useful Fourier transforms were obtained with X-band SAR as compared to L-band with equivalent signal-to-noise ratio and synthetic aperture resolution. A comparison between X-band wave images and the in situ measurements shows agreement in the dominant wave direction to within a few degrees. The normalized spectra show a striking resemblance in spectral shape.
    Keywords: OCEANOGRAPHY
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  • 6
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    On the relationship of radar backscatter to wind speed and fetch (1978)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: The physics of the interaction of electromagnetic waves with the ocean surface has been an active area of research for a number of years. This paper contains the results of satellite and aircraft experiments to investigate the ability of active microwave radars to infer surface wind speeds remotely. Data obtained from the recent National Aeronautics and Space Administration (NASA) Skylab experiment are compared with surface wind speeds measured by low-flying aircraft and ships-of-opportunity and found to give useful estimates of the ocean wind field. Also investigated was the influence of varying wave height on radar measurements of wind speed by measuring the backscattering cross-section for constant wind speed but variable wave conditions. It is found that this effect is of little importance.
    Keywords: OCEANOGRAPHY
    Format: text
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  • 7
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    Spectral characteristics of the microwave emission from a wind-driven foam-covered sea (1976)
    In:  Other Sources
    Details
    Publication Date: 2011-08-16
    Description: Aircraft observations of the microwave emission from the wind-driven foam-covered Bering Sea substantiate earlier results and show that the combination of surface roughness and white water yields a significant microwave brightness temperature dependence on wind speed over a wide range of microwave wavelengths, with a decreasing dependence for wavelengths above 6 cm. The spectral characteristic of brightness temperature as a function of wind speed is consistent with a foam model in which the bubbles give rise to a cusped surface between the foam and the sea. In the fetch-limited situation the contribution of the wave structure at the surface appears to increase as the foam coverage decreases. Although the data show that the thin streaks are the most important part of the white water signature, there is some evidence for the contribution of whitecaps.
    Keywords: OCEANOGRAPHY
    Type: Journal of Geophysical Research; 81; June 20
    Format: text
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  • 8
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    Vanadium K Xanes Studies of EET79001 Impact-Melt Glasses Revisited (2016)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Some impact-melt glasses in shergottites are rich in Martian atmospheric noble gases and sulfur suggesting a possible association with regolith-derived secondary mineral assemblages in the shocked samples. Previously, we studied two glasses, # 506 (Lith C in Lith A) and # 507 (Lith C in Lith B) from EET79001 [1,2] and suggested that sulfur initially existed as sulfate in the glass precursor materials and, on shock-melting of the precursors, the sulfate was reduced to sulfides in the shock glasses. To examine the validity of this hypothesis, we used V K microXANES techniques to measure the valence states of vanadium in the Lith C glasses from Lith A and Lith B in EET79001 [3] to complement and com-pare with previous analogous measurements on,78 glass (Lith C in Lith A) [4,5]. We reported the preliminary results in [3]. Vanadium is ideal for addressing the redox issue because it has multiple valence states and is a well-studied element. Vanadium in basalts exists mostly as V(sup 3+), V(sup 4+) and V(sup 5+) in terrestrial samples, mainly as V(sup 3+) with minor V(sup 2+) and minor V(sup 4+) in lunar samples and as roughly equal mixtures of V(sup 3+) and V(sup 4+) in Martian meteorites. In this report, we discuss the application of the V K XANES results to decipher the nature of shock reduction occurring in the silicate glasses during the impact process.
    Keywords: Geophysics
    Type: JSC-CN-35350 , Lunar and Planetary Science Conference; Mar 21, 2016 - Mar 25, 2016; The Woodlands, TX; United States
    Format: application/pdf
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  • 9
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    Al-Mg Isotope Study of Allende 5241 (2016)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The defining characteristic of type B1 CAIs is a large (.5- 3mm) concentric melilite mantle [1]. In [2] we presented two isochrons from separate traverses across the melilite mantle of Allende EK 459-5-1. The primary petrographic differences between the traverses was the preservation of strong oscillatory zoning. The traverse that crossed the distinctive oscillatory zone produced a pristine internal isochron, while the other that did not have a strongly preserved oscillatory zone produced a disturbed isochron indicated by more scatter (higher MSWD) and a positive (delta)26Mg* intercept. The implication simply being that the oscillatory zone may represent varying conditions during the mantle formation event. We targeted a similar texture in Allende 5241 using the same methodology in an attempt to achieve similar results.
    Keywords: Geophysics
    Type: JSC-CN-35195 , Lunar and Planetary Science Conference; Mar 21, 2016 - Mar 25, 2016; The Woodlands, TX; United States
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  • 10
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    CAIs in Semarkona (LL3.0) (2016)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Calcium, Aluminum-rich inclusions (CAIs) are the first forming solids of the Solar system. Their observed abundance, mean size, and mineralogy vary quite significantly between different groups of chondrites. These differences may reflect the dynamics and distinct cosmochemical conditions present in the region(s) of the protoplanetary disk from which each type likely accreted. Only about 11 such objects have been found in L and LL type while another 57 have been found in H type ordinary chondrites, compared to thousands in carbonaceous chondrites. At issue is whether the rare CAIs contained in ordinary chondrites truly reflect a distinct population from the inclusions commonly found in other chondrite types. Semarkona (LL3.00) (fall, ~691 g) is the most pristine chondrite available in our meteorite collection. Here we report petrography and mineralogy of 3 CAIs from Semarkona
    Keywords: Geophysics
    Type: JSC-CN-35196 , Lunar and Planetary Science Conference; Mar 21, 2016 - Mar 25, 2016; The Woodlands, TX; United States
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