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  • 1
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract We detected the loss of a MspI restriction site by a C to T transition at +83 bp and a G to A transition at +84 bp of the 5′-end non-coding region of the human apolipoprotein AI gene. This base change occurred at the “hot spot” (CCGG) for methylation, which may be important in the regulation of gene expression. The population frequency for the loss of the MspI site is 6.1%.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Physics Letters A 150 (1990), S. 277-280 
    ISSN: 0375-9601
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 82 (1991), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The long delayed maturation of the late metaxylem of maize (Zea mays) roots imposes a high-resistance barrier between the immature apices and the negative water potential of the leaves. These apices (20+ cm) bear strongly adhering soil sheaths to within 0.5 to 2 cm of the distal end. It was hypothesized that the sheathed immature apices should show less response to transpiration stress than bare regions. Measurements were made of the relative water content (RWC) of the sheathed and bare zones of the axile roots, both at different ages of the plant, and early and late in the day's transpiration. Sheathed roots maintained a steady RWC of about 83% irrespective of age or transpiration. Bare roots had RWCs of about 63% in the morning, but this fell to 55% in the afternoon. The first-order branches on the bare roots in the morning had still lower values of RWC, near 50%. Plots of RWC against water potential were indistinguishable for the three root types. It is concluded that the immature apices are indeed relatively isolated from the fluctuating tensions in the stem xylem, and that these tensions reduce the water content of bare roots and their branches to low values.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Neutron-diffraction techniques have been used to study the antiferromagnetic form factor of a La2NiO4 single crystal at 15 K. The antiferromagnetic form factor was obtained by measuring the integrated intensities of 16 magnetic reflections. A plateau is clearly seen at low Q (up to 3 A(ring)−1) in the experimentally determined form factor, similar to those observed for La2CuO4 and Sr2CuO2Cl2. As in the case of these latter compounds, the fit of the experimental data by a Ni2+ ionic form factor is not satisfactory. The experimental data are compared with a recent spin-polarized band calculation and with a covalency model.
    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 89 (2001), S. 7669-7671 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Studies of superconductivity and flux pinning were carried out on (Bi1.64Pb0.36)Sr2Ca1−xYxCu2O8+y (x=0, 0.05, 0.11, 0.33) single crystals grown by the self-flux method. X-ray diffraction, transport, and magnetic measurements were performed for purposes of characterization. X-ray analysis revealed that the c lattice parameter systemically decreases as the Y doping level increases. The superconducting transition temperature Tc decreases from 80 to 30 K as x increases. A strong annealing effect on Tc and superconducting volume has been observed. Resistance measurements show that x=0.33 samples are semiconductive over a wide temperature range between 4.2 and 300 K for the as-grown state, but become metallic with Tc of 65–70 K after air or oxygen annealing. Flux pinning was studied by measuring the hysteresis loop at different temperatures and different fields. A peak effect was observed in all the codoped samples. Results show that at low temperatures, the peak field is smaller than in solely Pb doped crystals and decreases as x increases (x〉0.1). However, the peak field at high temperature for the x=0.05 sample is higher than in heavily Pb doped Bi2212 crystals, indicative of a strong pinning due to the codoping. © 2001 American Institute of Physics.
    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 67 (1990), S. 4524-4526 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Neutron diffraction techniques have been used to study the antiferromagnetic form factor of Sr2CuO2Cl2, which has the body-centered-tetragonal (I4/mmm) K2NiF4-type structure (the same as that of tetragonal La2CuO4 but with the out-of-plane oxygens replaced by Cl and the La by Sr). The antiferromagnetic form factor was obtained at 15 K by measuring the integrated intensities of the ( (1)/(2) (1)/(2) 0), ( (1)/(2) (1)/(2) 2), ( (1)/(2) (1)/(2) 3), ( (3)/(2) (3)/(2) 0), ( (3)/(2) (3)/(2) 6), ( (3)/(2) (5)/(2) 1), ( (3)/(2) (3)/(2) 8), and ( (5)/(2) (5)/(2) 0) magnetic reflections of a single crystal of Sr2CuO2Cl2. The experimentally determined magnetic form factor is similar to that of La2CuO4. The experimental data were compared with the Cu2+ magnetic form factor and with the results of band theoretical calculations. We find that the fit to the experimental data is improved if one assumes a dipolar spin polarization on the in-plane oxygen ions.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 75 (1999), S. 3294-3296 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We demonstrate that the thermal expansion behavior of a material can be substantially modified by the presence of residual stresses. In the case of a composite tube made of two layers of dissimilar steels, in situ neutron diffraction measurements revealed a significant difference in the coefficients of thermal expansion along the radial and tangential directions. It is shown that the observed difference in thermal expansion is due to the change of residual stresses with temperature. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 80 (2002), S. 829-831 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Transport critical current (Ic) was measured for Fe-sheathed MgB2 round wires. A critical current density of 5.3×104 A/cm2 was obtained at 32 K. Strong magnetic shielding by the iron sheath was observed, resulting in a decrease in Ic by only 15% in a field of 0.6 T at 32 K. In addition to shielding, interaction between the iron sheath and the superconductor resulted in a constant Ic between 0.2 and 0.6 T. This was well beyond the maximum field for effective shielding of 0.2 T. This effect can be used to substantially improve the field performance of MgB2/Fe wires at fields at least three times higher than the range allowed by mere magnetic shielding by the iron sheath. The dependence of Ic on the angle between field and current showed that the transport current does not flow straight across the wire, but meanders between the grains. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 396-398 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Polycrystalline bulk porous samples with a large number of weak-link grain boundaries and high density polycrystalline bulk samples with strong-link boundaries were synthesized by conventional solid-state reaction and a partial melting technique. The weak-link samples showed large magnetoresistance (MR,Δρ/ρH=[ρ0−ρH]/ρ0), 20–30%, at a low magnetic field of 300 mT and over a wide temperature range from the magnetic transition at 235 to 77 K. The partially melted samples exhibited the same magnetoresistance behavior as that of single crystals with a maximum peak MR of 15% at a narrow temperature range around the ferromagnetic transition. It is suggested that grain boundaries are necessary but not sufficient to account for the MR at low field over a large temperature range. Weak-link grain boundaries rather than strong-link boundaries are responsible for the MR at low field over a large temperature range. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 6229-6233 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present photoconductivity data on GaAs quantum wires grown on a V-grooved substrate by flow rate modulation epitaxy. They show that a moderate excitation power density, ∼1 W/cm2, allows the observation of the absorption structure of a single GaAs quantum wire embedded in a p-i-n diode. Furthermore, by increasing the number of active wires inside a diode, the photoconductivity signal is enhanced and additional details of the absorption structure are evidenced. And, finally, a rough quantitative agreement is obtained between the experimental absorption transitions and a simple calculation of the one-dimensional excitonic states using the envelope function approximation. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
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