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  • 1
    Publication Date: 2022-05-25
    Description: Author Posting. © The Authors, 2010. This is the author's version of the work. It is posted here by permission of National Academy of Sciences for personal use, not for redistribution. The definitive version was published in Proceedings of the National Academy of Sciences of the United States of America 107 (2010): 14020-14025, doi:10.1073/pnas.1009205107.
    Description: Thirty years after the first discovery of high-temperature submarine venting, the vast majority of the global Mid Ocean Ridge remains unexplored for hydrothermal activity. Of particular interest are the world’s ultra-slow spreading ridges which were the last to be demonstrated to host high-temperature venting, but may host systems particularly relevant to pre-biotic chemistry and the origins of life. Here we report first evidence for diverse and very deep hydrothermal vents along the ~110 km long, ultra-slow spreading Mid-Cayman Rise. Our data indicate that the Mid- Cayman Rise hosts at least three discrete hydrothermal sites, each representing a different type of water-rock interaction, including both mafic and ultra-mafic systems and, at ~5000 m, the deepest known hydrothermal vent. Although submarine hydrothermal circulation, in which seawater percolates through and reacts with host lithologies, occurs on all mid-ocean ridges, the diversity of vent-types identified here and their relative geographic isolation make the Mid-Cayman Rise unique in the oceans. These new sites offer prospects for: an expanded range of vent-fluid compositions; varieties of abiotic organic chemical synthesis and extremophile microorganisms; and unparalleled faunal biodiversity - all in close proximity.
    Description: This research was funded through NASA (ASTEP) and WHOI (Ocean Ridge Initiative).
    Repository Name: Woods Hole Open Access Server
    Type: Preprint
    Format: application/pdf
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  • 2
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have measured electron paramagnetic resonance (EPR), resistivity, and dc susceptibility from 2 to 300 K for the oxide high Tc superconductors (R)Ba2Cu3Oy (R=Y,Pr,Nd,Eu,Gd,Ho,Er,Tm, or Yb). Selected systems were doped with 3-d ions (Cr,Mn,Fe,Ni,Co, or Zn) or 4-f ions (Gd or Er) which presumably substitute for the Cu or R site, respectively. In the systems studied we have observed an EPR line at low temperatures (T〈40 K), which exhibits an increase in intensity and decrease in field for resonance as the temperature is lowered. The ESR linewidth is also temperature dependent and exhibits a minimum at about 15 K. An additional EPR line that can be associated with a Gd3+, Mn2+ or Er3+ ion was observed for those samples where these ions were present as dilute impurities. In some of the samples another EPR signal is observed with properties that depend on sample preparation conditions. The behavior and origin of all lines will be discussed. The variation of Tc with concentration of the added impurities over the range (1%–15%) will also be presented, and compared with previous studies in other superconducting systems.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 72 (2001), S. 4201-4206 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We have analyzed the sources of error in the measurement of the Seebeck coefficient and designed a low frequency ac method to reduce them. This method has high precision in a short time period compared to commonly used dc methods while it minimizes some major sources of error that other ac methods do not. Furthermore, the setup can be fit into a 3 mm diam × 7 mm Teflon pressure cell and has minimal side effects due to the heat conductance of the pressure medium. We have also proposed and tested several methods to calibrate the Seebeck coefficient of thermocouples under pressure. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 5613-5615 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report magnetoresistance measurements of the heavy electron compound UBe13 above the superconducting transition temperature Tc and below 4 K for pressures P up to 19 kbar and for magnetic fields H up to 9 T. We observe strong negative magnetoresistance at all pressures and temperatures. The resistivity ρ is quadratic in temperature T from Tc up to a maximum temperature of 1 K at 1 bar increasing to 2 K at 19 kbar. The slope of the T2 term decreases with both H and with P. We find that δ(H)≡−[ρ(H)−ρ(0)]/ρ(0) for a given pressure scales as a function of H/T and exhibits power-law behavior over one decade with an exponent of 1.7. In addition, δ(H) at high pressure shows this same power law over a more limited H/T range.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 61 (1987), S. 3899-3903 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The proximity-Josephson effect (PJE) is a powerful general method of determining the symmetry of the pair wave function in exotic superconductors. The method is simple and relatively insensitive to the surface condition of the sample. A superconducting probe (S) of known pairing symmetry (typically Nb or Ta) is brought into contact with the sample (N). Observations and arguments based on the de Gennes boundary condition at the NS interface both indicate formation of a local, proximity-induced superconducting region of depth ξ in the sample (N) under the probe. The induced pairs have the same symmetry as those of S. The expected pair-phase dependence of the coupling energy between the pairs in N and S leads to a Josephson current Ic(T), which may be observed up to a junction critical temperature T* which is typically ∼0.8 of the Tc of S. When the measurement temperature falls below the bulk Tc of N (the exotic superconductor), a pair wave function of possibly different symmetry forms in the bulk of N and overlaps the induced pair wave function near the probe. Weak interactions between the induced and bulk pairs occur. In the case of UBe13 contacted with a Ta tip, the interaction weakly suppresses the induced pairs [which determine Ic(T)] leading to a reduction of the Josephson current at T〈Tc. This observation of a negative S-wave proximity effect in superconducting UBe13, in good agreement with a Ginzburg–Landau analysis, is strong evidence for triplet pairing in this heavy fermion compound.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 61 (1987), S. 4373-4375 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have investigated the source of the anisotropic susceptibility of UZn8.5 by preparing single crystals of UxTh1–xZn8.5 for small x. Preliminary indications are that anisotropic exchange, rather than crystal field effects, are responsible for the anisotropy, but possible impurity contributions to the (anisotropic) susceptibility of the ThZn8.5 do not permit a stronger statement. Further measurements for small x show that both the electronic specific heat and the susceptibility at low temperature are strongly enhanced, and that Kondo-type resistivity minima are observed. The enhancements are somewhat reduced in the concentrated system UZn8.5.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report specific heat and μSR measurements on Th (x =0.019) and/or B (y=0.03) substituted UBe13. The specific heat data show that either Th or B substitution reduces the Kondo temperature TK and increases the entropy at the superconducting transition by almost 20%, indicating an enhanced density of states. However, whereas μSR shows clear evidence for magnetic correlations for Th substitutions (0.019〈x〈0.043), no magnetism is observed for B substitutions. The enhanced specific heat jump in the B-substituted material is associated with a change in the superconducting properties as TK is reduced.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 5487-5489 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Superconducting UPt3 is characterized by a novel and complex magnetic field-temperature phase diagram, with two superconducting transitions at Tc1 and Tc2 in zero field. We have studied the effects of Pd and Y impurities on the zero field superconducting properties of UPt3. Resistance measurements show that both dopants increase the residual resistivity and decrease the spin fluctuation temperature in the normal state. Tc1 is depressed by both dopants, but more effectively by Pd. ||Tc1 − Tc2|| is essentially unaffected by Y doping, but increases dramatically with Pd doping.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report superconducting and mechanical properties of YBa2Cu3O7−δ (YBCO) thick films on Ni-based alloys with a textured yttria-stabilized zirconia (YSZ) buffer layer. The YBCO and YSZ layers were deposited by pulsed laser deposition and ion beam assisted deposition, respectively. It was found that the transport critical current density (Jc) correlates very well with the YBCO mosaic spread. Jc over 1×10 6 A/cm2 at 75 K and ∼1×107 A/cm2 at 4 K were obtained in the 1-μm thick YBCO films. Zero field critical current of 120 amps at 75 K was obtained in a 2-μm-thick and 1-cm-wide YBCO film. Angular dependence measurement revealed Jc peaks for both H(parallel)c and H(parallel)a-b. The peak for H(parallel)c implies additional pinning due to defects such as small angle grain boundaries or twin boundaries. Bending tests at 75 K showed that the YBCO thick films on the metallic substrates could sustain a strain of 0.4% and over 1% for tension and compression, respectively. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Journal of the American Chemical Society 25 (1903), S. 540-541 
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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