Search Results - (Author, Cooperation:D. C. Cook)

Showing 1 - 16 results of 16, query time: 0.24s Refine Results
  1. 1
    Staff View
    Publication Date:
    2015-03-15
    Publisher:
    American Association for the Advancement of Science (AAAS)
    Print ISSN:
    0036-8075
    Electronic ISSN:
    1095-9203
    Topics:
    Biology
    Chemistry and Pharmacology
    Computer Science
    Medicine
    Natural Sciences in General
    Physics
    Keywords:
    *Conservation of Natural Resources/economics ; *Ecosystem ; *Environment ; Guidelines as Topic ; Policy
    Published by:
    http://www.aaas.org/

    Latest Papers from Table of Contents or Articles in Press
  2. 2
    Staff View
    Publication Date:
    2014-08-21
    Publisher:
    Nature Publishing Group (NPG)
    Print ISSN:
    0028-0836
    Electronic ISSN:
    1476-4687
    Topics:
    Biology
    Chemistry and Pharmacology
    Medicine
    Natural Sciences in General
    Physics
    Keywords:
    Animals ; Bone and Bones/microbiology ; Europe/ethnology ; Genome, Bacterial/*genetics ; Genomics ; History, Ancient ; Human Migration/history ; Humans ; Mycobacterium tuberculosis/*genetics ; Peru ; Phylogeny ; Pinnipedia/*microbiology ; Tuberculosis/*history/*microbiology/transmission ; Zoonoses/*history/*microbiology/transmission
    Published by:
    http://www.nature.com/

    Latest Papers from Table of Contents or Articles in Press
  3. 3
    Dooling, T. A. ; Cook, D. C.

    [S.l.] : American Institute of Physics (AIP)
    Published 1991
    Staff View
    ISSN:
    1089-7550
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    The magnetic and crystalline properties of a plasma-sprayed coating of the microwave absorbing zinc-nickel ferrite, (Zn0.41Ni0.59 )Fe2O4 have been studied at 300 K using the Mössbauer effect and x-ray diffraction (XRD). Both techniques indicate that the plasma-sprayed material separated into two phases. The first is a nickel-rich phase with magnetic fields of 47.5 and 44.5 T at the tetrahedral and octahedral sites, respectively. The second is a zinc-rich phase, zinc meta-ferrite, having a small magnetic field of 4.2 T. The quadrupole splitting of this second phase is ΔE=0.34 mm s−1, which is the same as in pure nonmagnetic zinc ferrite. XRD analysis shows that the zinc-rich phase remains cubic with a0= 8.389 A(ring) and the zinc meta-ferrite phase is tetragonal with the same lattice parameters as the cubic phase except for one elongated axis given by c0 =8.488 A(ring). This is much larger than the spacing for any of the series of zinc-nickel ferrites. The isomer shift of the zinc meta-ferrite is 0.710 mm s−1, which indicates that a large fraction of Fe3+ was reduced during the spraying process. Annealing the sprayed coating at temperatures less than 400 °C converted the zinc meta-ferrite into a magnetic phase that now exhibits magnetic fields close to those in the nickel-rich phase. However, the large isomer shift remains, indicating that the ferrous iron is still present. XRD shows that the phase is now cubic. Annealing up to 650 °C gradually oxidized all of the Fe2+ in the material and restored the magnetic and crystalline properties of the plasma-sprayed coating to very close to those of the unsprayed ferrite.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.348027

    Articles: DFG German National Licenses
  4. 4
    Dooling, T. A. ; Cook, D. C.

    [S.l.] : American Institute of Physics (AIP)
    Published 1991
    Staff View
    ISSN:
    1089-7550
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    The Mössbauer effect has been used to study the microscopic magnetic properties of the cubic microwave ferrite (Zn0.41Ni0.59)Fe2O4 at 300 K. The magnetically split spectrum is broad and unresolved due to the overlap of the hyperfine magnetic fields at the tetrahedral and octahedral sites. This is caused by a distribution of magnetic fields at each site. The distribution is especially large and asymmetric at the octahedral site and is due to the fact that the iron atoms at this site are influenced by the presence of both iron and zinc at the tetrahedral site. The octahedral site is more sensitive to changes in the number of zinc neighbors than is the tetrahedral site. Assuming a random distribution of the zinc at the tetrahedral site, and knowing the fraction of zinc in the ferrite, the binomial distribution has been used to calculate the expected magnetic-field distribution at the octahedral site as a function of the number of zinc neighbors. These figures have been compared with the magnetic-field distribution profile determined from the fit to the Mössbauer spectrum. Sufficiently good agreement has been found to allow us to isolate the magnetic-field contribution due to most of the different numbers, between zero and six, of neighboring zinc atoms.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.348026

    Articles: DFG German National Licenses
  5. 5
    Oh, Sei J. ; Cook, D. C.

    [S.l.] : American Institute of Physics (AIP)
    Published 1999
    Staff View
    ISSN:
    1089-7550
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    The relative recoilless fraction (F-value) of each of six iron oxides, defined as the ratio of the recoil-free fractions of two different materials, was experimentally determined relative to hematite at 300 K and 77 K by Mössbauer spectroscopy. Using the relative recoil-free fractions compared to that of hematite, the relative recoilless fractions between all pairs of the seven iron oxides were determined. The F-values can allow conversion of Mössbauer subspectral areas to the relative atomic, molecular, or weight fractions of each iron oxide present in a mixed oxide phase sample. © 1999 American Institute of Physics.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.369451

    Articles: DFG German National Licenses
  6. 6
    Cook, D. C.
    Springer
    Published 1988
    Staff View
    ISSN:
    1572-9540
    Source:
    Springer Online Journal Archives 1860-2000
    Topics:
    Physics
    Notes:
    Abstract A CEMS and XMS study of carbon steel has shown that the microstructure of the bulk material as well as the surface depends on the temperature at which the steel was tempered. Ion milling of the surface results in no change to the surface microstructure which corresponds closely to the bulk properties. However, after polishing the surface with 3μm diamond, the surface composition is changed to a large extent. Polishing decreases the amount of retained austenite and also the fraction of interstitial carbon within the austenite on the surface of the non-tempered steel. A related increase in the amount of surface martensite is observed. The effects of polishing extends to depths of over 1000 Å. Both X- and θ-carbides are present in each of the tempered steels and only the amount of θ-carbide is seen to increase as the samples are tempered to decrease hardness. Tempering to higher temperatures decreases the martensite content and a corresponding increase is seen in the θ-carbide only. Polishing also removes a large feaction of the carbide from the surface and this may account for the anomalously high wear resistance previously determined for the steel.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1007/BF02400468

    Articles: DFG German National Licenses
  7. 7
    Ruggiero, N. G. ; Cook, D. C. ; Edelstein, A. S.
    Springer
    Published 1990
    Staff View
    ISSN:
    1572-9540
    Source:
    Springer Online Journal Archives 1860-2000
    Topics:
    Physics
    Notes:
    Abstract We have studied the magnetic hyperfine interactions in GdAl3 using155Gd Mössbauer spectroscopy between the temperatures of 4K and 90K. Previous studies on GdAl3 have shown that antiferromagnetic ordering occurs at 18K, and that a fit of the susceptibility to 1/(T-θp) yields a θp value of −89K. The large ratio of θp to TN is indicative of magnetic frustration between competing ferro-and antiferromagnetic interactions, which may be due to a combination of the oscillatory nature of the RKKY interaction and the geometry of the hexagonal lattice. Our studies show that the saturation magnetic hyperfine field at the Gd site is −24.0 T, with the moments lying in the basal plane. The efg at the gadolinium site is 2.55(1)×1017V cm−2 which is considerably larger than the value predicted by a point charge calculation. This difference may indicate that there is a conduction electron contribution. A helical magnetic structure has been calculated from RKKY theory.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1007/BF02396113

    Articles: DFG German National Licenses
  8. 8
    Cook, D. C. ; Cashion, J. D.
    Springer
    Published 1977
    Staff View
    ISSN:
    1572-9540
    Source:
    Springer Online Journal Archives 1860-2000
    Topics:
    Physics
    Notes:
    Abstract From Mössbauer spectra of GdAlO3 and GdVO4 above and below the Néel temperature and fitted using a transmission integral, we have determined the following parameters of the 86.5 keV and 105 keV levels:g(86)/g(0)=+1.217±0.005,Q(86)/Q(0)= +0.10±0.02,g(105)/g(0)=−0.55±0.02,Q(105)/Q(0)=+0.74±0.02, Δ〈r 2〉105/ Δ〈r 2〉86=+1.30±0.05. The linewidth observed for the 105 keV transition is less than the calculated natural linewidth.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1007/BF01021716

    Articles: DFG German National Licenses
  9. 9
    Cook, D. C. ; Rawers, J. C.
    Springer
    Published 1994
    Staff View
    ISSN:
    1572-9540
    Source:
    Springer Online Journal Archives 1860-2000
    Topics:
    Physics
    Notes:
    Abstract A study has been made of highly nitrogenated pure iron and iron-aluminum alloy powder containing 2 wt.% Al (Fe-2Al) using Mössbauer spectroscopy and X-ray diffraction. The samples were prepared by high-temperature, high-pressure diffusion of nitrogen. They were prepared in a hot-isostatic-pressure (HIP) furnace at 1000 °C at nitrogen pressures up to 200 MPa. The alloy powders contained up to 8 at.% nitrogen as determined by vacuum fusion analysis. XRD analysis indicates that for the pure iron powders, the lattice spacing remained independent of nitrogen concentration, but that for the Fe-2Al powders, it decreased with increasing nitrogen concentration. Mössbauer analysis showed that for the pure iron powders, most of the nitrogen was associated with the formation of the iron nitride Fe4N. For the alloy powders containing less than 5 at.% nitrogen, all of the nitrogen was contained interstitially. The presence of nitrogen completely eliminated the conduction-electron spin-density oscillations observed in many ferromagnetic alloys.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1007/BF02065719

    Articles: DFG German National Licenses
  10. 10
    Grant, R. G. ; Cook, D. C.
    Springer
    Published 1994
    Staff View
    ISSN:
    1572-9540
    Source:
    Springer Online Journal Archives 1860-2000
    Topics:
    Physics
    Notes:
    Abstract Mössbauer spectroscopy and XRD were employed to characterize the microstructural properties of iron-zinc binary alloys between 0–31 at.% Fe. Samples were prepared with accuracies of ±0.5 at.% Fe, and the Mössbauer and lattice parameters were monitored as a function of iron concentration across each phase. Two iron sites were observed in the Γ phase (18–31 at.% Fe), whose occupancies and isomer shifts varied continuously with iron content. However, the quadrupole splitting of each site remained constant. Within the Γ1 phase (19–24 at.% Fe), three iron sites were observed whose isomer shifts and quadrupole splittings remained constant, while their occupancies varied with iron concentration. For the first time, a third iron site was observed in the δ phase (8–13 at.% Fe), whose occupancy increases with iron content. Also, the site occupancies of the two other δ sites appear to remain constant, while other Mössbauer parameters vary continuously with iron content. Analysis of the ζ phase (6–7 at.% Fe) showed the presence of one iron site, whose parameters were not observed to change due to the small variance in iron concentration. XRD studies indicate the lattice parameters across the Γ and δ phases vary continuously with iron concentration. Moreover, a better understanding of these phases, as formed in galvanneal steel coatings, was obtained.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1007/BF02063780

    Articles: DFG German National Licenses
  11. 11
    Cook, D. C.
    Springer
    Published 1986
    Staff View
    ISSN:
    1572-9540
    Source:
    Springer Online Journal Archives 1860-2000
    Topics:
    Physics
    Notes:
    Abstract A gas flow proportional counter has been constructed for operation between 100K and 400K without the need for an evacuated cryostat. The detector is temperature controlled and may be used for detecting conversion electrons or X-rays. Six different gases, pure He, He/1%CH4, He/5%CH4, He/10%CH4, He/5%Co, and Ar/5%CH4 have been investigated in order to obtain maximum efficiency and reliability of operation. At room temperature and above, all gases are suitable. At low temperatures, He/5%Co is the most suitable for electron detection, For X-ray detection, Ar/5%CH4 is suitable over the entire temperature range.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1007/BF02399510

    Articles: DFG German National Licenses
  12. 12
    Ford, D. J. ; Cook, D. C. ; Gardner, J. A. ; Sommers, J. A.
    Springer
    Published 1994
    Staff View
    ISSN:
    1572-9540
    Source:
    Springer Online Journal Archives 1860-2000
    Topics:
    Physics
    Notes:
    Abstract Superconducting YBa2Cu2.955Fe0.045O7 has been studied at temperatures between 300 and 1000 K. Spectra were recorded on a sample which was sealed as a pellet pressed with boron nitride. An atmosphere of oxygen was maintained in the sample region at all times. At temperatures up to 900 K, we observed the four iron sites A, (Cu(1) chain-site; square planar oxygen coordination with O(5) vacancy on thea-axis), B, (Cu(2) plane-site; square pyramidal oxygen coordination), C, (Cu(1) chain-site; square pyramidal oxygen coordination with O(5) site occupied) and D, (Cu(1) chain-site; quasi-tetrahedral oxygen coordination with O(4) vacancy along theb-axis). At temperatures up to 700 K, the relative area of the B and C sites remained nearly constant as the temperature was increased. However, the area of the A site decreased while, the D site area increased with increasing temperature. At all times, the total area of sites A and D remained constant, thereby indicating the possibility of oxygen atom hopping in thea-b plane. The quadrupole splitting of each site, except the B site, decreased linearly with increasing temperature.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1007/BF02072919

    Articles: DFG German National Licenses
  13. 13
    Cook, D. C. ; Li, Jun
    Springer
    Published 1986
    Staff View
    ISSN:
    1572-9540
    Source:
    Springer Online Journal Archives 1860-2000
    Topics:
    Physics
    Notes:
    Abstract The Mossbauer Effect study of polycrystalline Gadolinium Iron Garnet has been undertaken between 714K and 4.2K. The temperature dependence of the sublattice magnetization has been determined at the two iron sites and the direction of the hyperfine fields at each site is [111] over the entire temperature range. The saturation fields at the octahedral and tetrahedral sites are respectively 547 kOe and 477 kOe. The ferrimagnetic Neel temperature has been found to be 562.5K and above this temperature, the quadrupole splitting at the octahedral and tetrahedral sites are −0.43 mms−1 and ¦0.89¦mms−1 respectively.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1007/BF02061495

    Articles: DFG German National Licenses
  14. 14
    Cook, D. C.
    Springer
    Published 1986
    Staff View
    ISSN:
    1572-9540
    Source:
    Springer Online Journal Archives 1860-2000
    Topics:
    Physics
    Notes:
    Abstract The study of the corrosion products formed on the surface of Type 316 stainless steel exposed to chlorinated seawater for 18 days shows that ferrihydrite and lepidocrocite are the first oxides to form. The surface also shows the formation of a martensite when it is cleaned by light brushing before exposure. Samples of weathering steel, ASTM A242 Type 1, exposed for 51/2 years to either a marine or inland rural environment have been studied between 100K and 400K using CEMS and XMS. Different amounts of hydroxoxides are present on the surface of each sample. The steel exposed to the inland environment contains more α-FeOOH.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1007/BF02061587

    Articles: DFG German National Licenses
  15. 15
    Rezaie-Serej, S. ; Cook, D. C.
    Springer
    Published 1988
    Staff View
    ISSN:
    1572-9540
    Source:
    Springer Online Journal Archives 1860-2000
    Topics:
    Physics
    Notes:
    Abstract A CEMS and XMS study of the surface oxidation of weathering steel, ASTM A242 Type 1, has shown that after exposure times of 5 1/2 years in a marine or industrial environment, the steel has not yet reached a stage at which the surface is fully protecting the substrate from further corrosion. The formation of α-FeOOH, an intermediate stage of protection, occurs mainly in the form of small particles, the properties of which exhibit an appreciable amount of superparamagnetic relaxation. For the steel exposed to a more moist marine environment, α-FeOOH exists only in the form of small particles. However for the steel exposed to a much dryer and corrosive industrial environment, more α-FeOOH is present. The formation of bulk α-FeOOH is more complete. The temperature dependence of the superparamagnetic hyperfine field and also the field distributions indicate that, in a marine environment, the clusters of α-FeOOH are both smaller in size and have a larger distribution of particle size. The XMS results indicate that α-FeOOH is present below a layer of γ-FeOOH and ferrihydrite which are generally accepted to constitute the early oxidation phases observed on steels.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1007/BF02400487

    Articles: DFG German National Licenses
  16. 16
    Cook, D. C. ; Tuszynski, R. S. ; Townsend, H. E.
    Springer
    Published 1990
    Staff View
    ISSN:
    1572-9540
    Source:
    Springer Online Journal Archives 1860-2000
    Topics:
    Physics
    Notes:
    Abstract Mössbauer spectroscopy has been used to identify the zinc-iron intermetallic phases present in the coating of three galvannealed steels, two of which were produced on commercial galvanizing lines and one in the laboratory. Both CEMS and XMS have been used in order to determine the depth dependence of each phase. Three main zinc-iron phases have been identified with the proportion of each dependent on the preparation conditions. In the commercially produced coatings, CEMS, probing near the top of the coating, indicates that the zinc rich χ-FeZn13 and δ-FeZn10 alloys are present. XMS indicates the presence of some Π-Fe3Zn10 closer to the steel. In contrast, the laboratory produced sample contains nearly pure χ-FeZn13 through the entire coating thickness. Subphases of the delta and gamma alloys were also identified. These subphases appear to be mixed with a preference for the higher zinc subphase of each to form closer to the surface of the coating.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1007/BF02396128

    Articles: DFG German National Licenses