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  • 1
    Electronic Resource
    Electronic Resource
    Layered manganites: Magnetic structure at extreme doping levels (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 4352-4354 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report powder neutron diffraction results on the crystal and magnetic structures of the bilayer Ruddlesden–Popper phase Sr3Mn2O7−δ (δ=0.0, 0.45) and correlate these structures with their magnetic and transport properties. The δ=0.45 compound contains a large number of oxygen vacancies that are disordered in the MnO2 planes. As a result of this disordered vacancy structure, Sr3Mn2O6.55 is a nonmagnetic insulator. Sr3Mn2O7.0 (δ=0) is an antiferromagnetic insulator whose magnetic structure is related to that of the SrMnO3 perovskite. Comparison of this end-member compound to its doped congeners in the La2−2xSr1+2xMn2O7 series highlights the extreme sensitivity of magnetic structure to dopant concentration in these layered materials. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.370498
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  • 2
    Electronic Resource
    Electronic Resource
    FETOMATERNAL BLEEDING DURING ATTEMPTS AT EXTERNAL VERSION (1980)
    Oxford, UK : Blackwell Publishing Ltd
    BJOG 87 (1980), S. 0 
    Details
    ISSN: 1471-0528
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The frequency and size of fetomaternal bleeds during the first attempt at external version of the fetus in breech presentation in 50 pregnant women were investigated. Fetomaternal bleeds of 0–1 to 1–5 ml were detected in 14 women (28 per cent). It is concluded that rhesus negative women should be given anti-D before attempts at external version are made.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-0528.1980.tb05005.x
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  • 3
    Electronic Resource
    Electronic Resource
    Code-switching as a communication, learning, and social negotiation strategy in first-year learners of Danish (2003)
    Oxford, UK and Boston, USA : Blackwell Publishing Ltd
    International journal of applied linguistics 13 (2003), S. 0 
    Details
    ISSN: 1473-4192
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Linguistics and Literary Studies
    Notes: The term ‘code-switching’ is used in two related yet different fields of linguistics: second language acquisition and bilingual studies. In the former, code-switching is analyzed in terms of learning strategies, whereas the latter applies a competence view. This article intends to detect the borderline between the two concepts by investigating the use of code-switching in first-year learners of Danish. Our study points out that code-switching appears as a skill used in early attempts of playing with the languages involved in the conversation (Danish/English and Danish/Polish/German/English). Thus we have to acknowledge code-switching as an increasingly sophisticated language skill even at an early stage of SLA.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/1473-4192.00036
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  • 4
    Electronic Resource
    Electronic Resource
    Pressure-induced phase transition and pressure dependence of crystal structure in low (α) and Ca/Al-doped cristobalite (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 1361-1367 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The phase stability and atomic-level compression mechanisms for both SiO2 cristobalite, and for cristobalite partially stabilized by Ca/Al doping (Cax/2 Si2−xAlxO4), have been investigated. A phase transition to a lower symmetry phase, observed with in situ high-pressure energy-dispersive x-ray diffraction, occurs at about 1.2 GPa. Structure models of the low-pressure phase were obtained by Rietveld analysis of neutron powder-diffraction data from powdered samples contained in a gas pressure apparatus. These data were collected at pressures up to 0.6 GPa and at 298 and 60 K. The results suggest collapse of the corner-connected framework from rotations of the rigid SiO4 tetrahedra at high pressures and low temperatures as the dominant mechanism for the densification of both materials. Compared to pure SiO2 cristobalite at the same pressure and temperature, the Ca/Al-doped material has a larger unit-cell volume. It also has a larger Si-O-Si bending angle and a more expanded framework as evidenced by the smaller rotations of the rigid SiO4 tetrahedra. The rate of change of these parameters as a function of pressure and temperature is the same for both pure and Ca/Al-doped cristobalite. These observations are consistent with Ca occupying positions within the cavities formed by the (Si, Al)-O framework and bracing it against collapse.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356415
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  • 5
    Electronic Resource
    Electronic Resource
    Superconductivity in YBa2−xSrxCu3O7−δ (1987)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 51 (1987), S. 279-281 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report structure, resistivity, and Meissner effect measurements on YBa2−xSrxCu3O7−δ for 0〈x〈2.0. We find a region of solid solubility extending at least to x=1.0 and a monotonic depression of Tc with x. Using arguments based on structural changes with Sr doping, we speculate that the depression of Tc is due to the local distortion of the lattice in the neighborhood of the Sr site and the introduction of additional oxygen vacancies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.98472
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  • 6
    Electronic Resource
    Electronic Resource
    Pressure-induced cubic-to-orthorhombic phase transformation in the negative thermal expansion material HfW2O8 (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 3184-3188 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effect of pressure on the crystal structure of HfW2O8 has been investigated by neutron powder diffraction. At a hydrostatic pressure of 0.62 GPa at room temperature the cubic material transforms, with a 5% reduction in volume, to the same orthorhombic phase that is seen in the isostructural compound ZrW2O8 above 0.21 GPa. The transformation is sluggish, requiring about 24 h to complete at constant pressure. Once formed, the orthorhombic phase is retained upon release of pressure. Upon heating to 360 K, the metastable orthorhombic phase transforms back to the cubic phase. The substantially higher pressure for the cubic-to-orthorhombic transition in HfW2O8, compared to ZrW2O8, may be important for the application of this material in composites with controlled thermal expansion because rather large local pressures can occur in such composites. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1347412
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  • 7
    Electronic Resource
    Electronic Resource
    Magnetic structure of UCu2Si2 and U(Cu0.75Mn0.25)2Si2 (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 3604-3605 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The replacement of Cu by Mn in UCu2Si2 causes surprisingly large increases in both the Curie temperature and the coercivity of this ferromagnetic material. We have performed neutron powder diffraction experiments on a series of U(Cu,Mn)2Si2 alloys and found that UCu2Si2 is a simple ferromagnet with a magnetic moment of 2.0(1)μB on the U atoms pointing along the crystallographic c axis of the tetragonal unit cell. The alloy U(Cu0.75Mn0.25)2Si2 is also a ferromagnet with moments on both U and Mn pointing in the c direction. The moment on the U atoms is 1.7(1)μB, and the average moment on the (Cu,Mn) site is 0.16(5)μB. No indication of chemical ordering on the (Cu,Mn) site was detected.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.340708
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  • 8
    Electronic Resource
    Electronic Resource
    Magnetic ordering and crystal field effects in REBa2Cu3O7−x (RE=Gd, Dy, Ho, Er) (abstract) (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 4202-4202 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Heat capacity, resistivity and magnetic susceptibility data have been used to study electronic and magnetic properties of REBa2Cu3O7−x compounds. Neutron diffraction on the Ho compound shows identical crystal structure to YBa2Cu3O6.8. All the compounds are superconducting at Tc=(93±2) K. Magnetic transitions are observed in the heat capacity data at Tm=2.2, 0.95, 0.17, and 0.59 K for RE=Gd, Dy, Ho, and Er, respectively, and the magnetically ordered state is found to coexist with superconductivity. Estimates have been obtained for the magnetic moment in the crystal field ground state and the energy splitting of the first excited state crystal field level.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.340225
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  • 9
    Electronic Resource
    Electronic Resource
    The irreversibility line of HgBa2CuO4+δ (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 63 (1993), S. 693-695 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Using magnetization hysteresis loops we have determined the irreversibility line of polycrystalline samples of HgBa2CuO4+δ and Hg0.8Pb0.2Ba2CuO4+δ. The irreversibility line is found at rather high temperatures. It does not show the drastic depression with increasing temperature as is observed in highly anisotropic Bi/Tl-based CuO superconductors. At 77 K the irreversibility field is around 0.3 T, which is substantially higher than in Bi2Sr2CaCu2O8 and Bi2Sr2Ca2Cu3O10. The advantages of this material for large-scale applications are outlined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.109931
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  • 10
    Electronic Resource
    Electronic Resource
    Sequential immunophenotypic study of lymphoid infiltrate in allergic and irritant reactions (1987)
    Oxford, UK : Blackwell Publishing Ltd
    Contact dermatitis 16 (1987), S. 0 
    Details
    ISSN: 1600-0536
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Sequential biopsies (4–72 h) of early allergic and irritant patch test reactions have been examined immunohistologically for reactivity with 19 monoclonal antibodies against antigens on lymphoid cells in order to investigate the nature/origin of the infiltrating lymphoid cells and assess their state of activation/proliferation. The composition of the infiltrates was similar in allergic and irritant reactions and consisted of T-lymphocytes of helper/inducer types in association with T-cell accessory cells, i.e., Langerhans cells and HLA-DR-positive macrophages. No differences in expression of T-cell or macrophage associated antigens were seen in early as opposed to late biopsies. In contrast, the proportion of cells positive for markers associated with activation (interleukin-2 receptor) or proliferation (transferrin receptor, the Ki-67 nuclear antigen) of lymphoid cells was found to increase with time in both types of reaction. These data substantiate the view that T-cell immune reactions are implicated in both allergic and toxic patch test lesions, and indicate that the lymphocytes in the infiltrates are activated and proliferate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1600-0536.1987.tb01445.x
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