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  • 1
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    PANGAEA
    In:  Supplement to: Bechshøft, Thea Ø; Sonne, Christian; Dietz, Rune; Born, Erik W; Novak, M A; Henchey, E; Meyer, J S (2011): Cortisol levels in hair of East Greenland polar bears. Science of the Total Environment, 409(4), 831-834, https://doi.org/10.1016/j.scitotenv.2010.10.047
    Publication Date: 2023-12-13
    Description: To demonstrate the ability to assess long-term hypothalamic-pituitary-adrenocortical (HPA) axis activity in polar bears (Ursus maritimus), a pilot study was conducted in which cortisol concentration was analyzed in hair from 7 female (3-19 years) and 10 male (6-19 years) East Greenland polar bears sampled in 1994-2006. The hair was chosen as matrix as it is non-invasive, seasonally harmonized, and has been validated as an index of long-term changes in cortisol levels. The samples were categorized according to contamination: eight were clean (2 females, 6 males), 5 had been contaminated with bear blood (2 F, 3 M), and 4 with bear fat (3 F, 1 M). There was no significant difference in cortisol concentration between the three categories after external contamination was removed. However, contaminated hair samples should be cleaned before cortisol determination. Average hair cortisol concentration was 8.90 pg/mg (range: 5.5 to 16.4 pg/mg). There was no significant correlation between cortisol concentration and age (p = 0.81) or sampling year (p = 0.11). However, females had higher mean cortisol concentration than males (females mean: 11.0 pg/mg, males: 7.3 pg/mg; p = 0.01). The study showed that polar bear hair contains measurable amounts of cortisol and that cortisol in hair may be used in studies of long-term stress in polar bears.
    Keywords: Age, relative, number of years; Cortisol; East_Greenland; East Greenland; International Polar Year (2007-2008); IPY; Sampling date; Sex; Status
    Type: Dataset
    Format: text/tab-separated-values, 135 data points
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  • 2
    facet.materialart.
    Unknown
    PANGAEA
    In:  Supplement to: Bechshøft, Thea Ø; Rigét, Frank F; Sonne, Christian; Letcher, Robert J; Muir, Derek C G; Novak, M A; Henchey, E; Meyer, J S; Eulaers, I; Jaspers, Veerle LB; Eens, Marcel; Covaci, Adrian; Dietz, Rune (2012): Measuring environmental stress in East Greenland polar bears, 1892-1927 and 1988-2009: What does hair cortisol tell us? Environment International, 45, 15-21, https://doi.org/10.1016/j.envint.2012.04.005
    Publication Date: 2023-12-13
    Description: Hair sampled from 96 East Greenland polar bears (Ursus maritimus) over the periods 1892-1927 and 1988-2009 was analyzed for cortisol as a proxy to investigate temporal patterns of environmental stress. Cortisol concentration was independent of sex and age, and was found at significantly higher (p〈0.001) concentrations in historical hair samples (1892-1927; n = 8) relative to recent ones (1988-2009; n = 88). In addition, there was a linear time trend in cortisol concentration of the recent samples (p〈 0.01), with an annual decrease of 2.7%. The recent hair samples were also analyzed for major bioaccumulative, persistent organic pollutants (POPs). There were no obvious POP related time trends or correlations between hair cortisol and hair POP concentrations. Thus, polar bear hair appears to be a relatively poor indicator of the animal's general POP load in adipose tissue. However, further investigations are warranted to explore the reasons for the temporal decrease found in the bears' hair cortisol levels.
    Keywords: Dichlorodiphenyldichloroethylene, standard deviation; East_Greenland; East Greenland; International Polar Year (2007-2008); IPY; Oxychlordane; para,para-Dichlorodiphenyldichloroethylene; Polybrominated diphenyl ethers, congener BDE-47; Polybrominated diphenyl ethers, standard deviation; Polychlorinated biphenyl, standard deviation; Polychlorinated biphenyl 138; Polychlorinated biphenyl 153; Polychlorinated biphenyl 156; Polychlorinated biphenyl 170; Polychlorinated biphenyl 180; Polychlorinated biphenyl 183; Polychlorinated biphenyl 187; Standard deviation; trans-Nonachlor
    Type: Dataset
    Format: text/tab-separated-values, 44 data points
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  • 3
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Magnetic relaxation experiments constitute a unique method of determining the nature of fluctuations in dissipative magnetic systems. At high temperatures these fluctuations are thermal and strongly temperature dependent. At low temperatures, where quantum fluctuations dominate, magnetic relaxation becomes independent of temperature. Such behavior has been observed in many systems. In this review we emphasize the study of low temperature relaxation in ferromagnetic nanoparticles, layers, and multilayers (including "domain wall junctions''), and large single crystals. The results of magnetic relaxation experiments are shown to agree with theoretical predictions of quantum tunneling of the magnetization. When dissipation becomes important, in large and complex systems, a time dependent WKB exponent needs to be introduced.
    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 87 (2000), S. 6004-6006 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present a comparison of the field dependence of the relaxation times observed for Mn12Bz, (Bz=benzoate) spin cluster, and its derivative containing one extra electron, r-Mn12Bz. At low temperatures Mn12Bz has a total spin S=10, while for the reduced sample r-Mn12Bz the spin of the ground state is S=19/2. Theory predicts that half integer spin should not present quantum tunneling, the so-called spin parity effect. We show evidence from experiments that quantum tunneling is partially inhibited in the reduced species. Low temperature magnetization hysteresis loops of the reduced variety do not show well-defined steps. In addition, the ac susceptibility as a function of the field also does not show a clear resonance at the expected level crossing fields, as seen in the nonreduced sample. © 2000 American Institute of Physics.
    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 63 (1988), S. 5044-5047 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Thermal diffusivity results for superconducting YBa2Cu3O7−x systems are reported. Two laser excitation techniques were used: photoacoustic phase-lag and the flash method. We observed an anomalous jump in the thermal diffusivity at the critical temperature and related it to the electronic specific heat anomaly. This correlation yielded a characteristic phonon frequency of 320 cm−1 in the range of an active Raman mode already observed in a single crystal of the same compound. This result reinforces the current electron-phonon coupling mechanism as responsible for superconductivity.
    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 57 (1985), S. 3418-3420 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Magnetization measurements down to 10 mK of Cd1−xMnxTe for Mn concentrations 0.01≤x≤0.15 show spin glass behavior. Such behavior is attibuted to short-range exchange and dipolar interactions. Both interactions are used to explain the concentration dependence of the spin freezing temperatures for 0.01≤x≤0.6, the short-range exchange dominating at high concentrations, and the dipolar interaction at low concentrations.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 6943-6945 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The magnetic properties of the Mn12ac molecular cluster were studied by complex susceptibility and specific heat measurements. Extensive ac susceptibility measurements done under a magnetic field on good quality single crystals and zero field powder sample specific heat results indicate that the usual uniaxial Hamiltonian, as well as the recently proposed fourth order corrections, are not enough to account for all the observations. Very low temperature specific heat data indicate the presence of zero field splitting of the ground state which is much larger than expected. Finally, specific heat measurements done under a magnetic field permitted us to observe and measure the lattice spin relaxation by calorimetric methods with time constants that are in agreement with the magnetic relaxation measurements. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 365 (1993), S. 141-143 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The structure7 of Mn12 is sketched in Fig. 1. The cluster has an overall D2d symmetry. The manganese (in) ions define the external octagon, whereas the manganese (iv) ions correspond to the internal tetrahedron. In the crystal lattice all the molecules have the S4 symmetry axis parallel to the ...
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 363 (1993), S. 147-149 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] This biradical (Fig. \a) was prepared because an intra-molecular ferromagnetic interaction between the two orthogonal N-O groups of the molecule could be expected on symmetry considerations (an unpaired electron is nearly localized on each NO radical)9'10. In the crystal (Table 1; Y. Dromzee, Y. ...
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Archives of environmental contamination and toxicology 17 (1988), S. 699-710 
    ISSN: 1432-0703
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Notes: Abstract Concentrations of polychlorinated biphenyls (PCBs) in the Hudson River were monitored from 1978 through 1985, by chromatographic analysis of the tissue residues of hydropsychid caddisflies and the contents of artificial substrate samplers. For both means of assessment, levels of Aroclor® 1016 and Aroclor® 1254 were positively correlated. Temporally, PCB concentrations decreased at all sampling stations from 1978 to 1980, but increased and remained stable from 1981 through 1985. Spatially, PCB levels as measured by artificial substrate samplers, decreased along the length of the river. Spatial trends in caddisflies were not as consistent as those of the artificial substrate samplers; in 6 of the 8 years sampled, there was no significant decrease in PCB concentrations in caddisflies from the point of discharge of the contaminant to the most downstream sampling site.
    Type of Medium: Electronic Resource
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