Library

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    Neutron scattering investigation of the ordered state of the nuclear spins in Cu at 60 nK (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 5433-5435 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have studied the magnetic structure of the nuclear spin system in Cu below 60 nK by means of neutron scattering. The observation of the nuclear (100) superlattice reflection proves the theoretically predicted antiferromagnetic arrangement of the nuclear spins. The critical field at the lowest temperatures was 0.24 mT. Around 0.1 mT the (100) reflection could not be observed. This is taken as an indication for, possibly, a reorientation phase transitition at this field. Therefore, the phase diagram contains at least two phases. For 0.1 mT〈B〈0.24 mT strong time dependencies of the ordering were observed. At low fields (B〈0.1 mT) nucleation times of the order of 10 s have been observed. These results are discussed with respect to the cooling technique: Adiabatic demagnetization requires constant entropy, a rather unusual way to bring a system from the paramagnetic to the ordered phase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.344580
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Neutron scattering studies of the spin dynamics in nonlinear and Haldane systems (invited) (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 5593-5598 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In 1D magnets contributions to the spin dynamics which are outside the scope of spin-wave theory can be studied theoretically as well as experimentally. Two prominent examples of such effects are discussed here: solitons and the Haldane gap. We discuss inelastic polarized neutron scattering results on the stability of solitons in CsNiF3 and on the existence of the Haldane gap in CsNiCl3. In both cases, the separate determination of the different correlation functions 〈SαSα〉 with α=x,y,z is essential for definite conclusions: Solitons in CsNiF3 appear to be much more stable than expected from classical theories, and the Haldane gap is the only explanation for the observed gaps in CsNiCl3.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.345895
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    n-ZnO/p-CdSiAs2 heterojunction solar cells (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 1560-1561 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Heterojunction solar cells were prepared by magnetron sputtering of n-ZnO onto p-CdSiAs2 single crystals. These crystals were grown by chemical vapor-phase transport and have a resistivity of 2 Ω cm, a Hall mobility of 300 cm2/V s, and a net carrier density of 1016 cm−3 at room temperature. The heterojunctions exhibit short-circuit current densities up to 12 mA/cm2 and open-circuit voltages between 180 and 250 mV with power conversion efficiencies up to 1% under 72 mW/cm2 halogen lamp illumination. Open-circuit voltage values could be increased by heat treatment at 80 °C for 15 min in an argon atmosphere. By measuring the reflection and the quantum yield versus wavelength the efficiency losses in the short-wavelength region could be attributed to the corresponding high reflection.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.341835
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Thin-film CdSe: Photoluminescence and electronic measurements (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 2601-2606 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The electronic properties of thin CdSe films prepared through physical vapor transport were investigated using photoluminescence (PL) and electronic measurements. The films were studied at each of the main preparation steps, i.e., evaporation, annealing, etching, and finally photoetching. At 3 K two distinct donor-acceptor (DA) transitions at 1.75 and 1.70 eV were found in the photoluminescence spectra in addition to deep states at about 1.55 eV at 20 K. These DA transitions which are produced mainly during the evaporation might be associated with group VII and with alkali metal impurities. After each preparation step the DA transitions change their intensities. It is shown that photoetching of the films leads to a removal of the deep centers, while the 1.75 eV transition is blue shifted. In contrast with single-crystal CdSe the intensity of the PL increases after photoetching. The results of the PL are consistent with the electronic measurements. They are explained in terms of a previously published model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.341649
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Ultrastructure of monkey (Macaca radiata) spermatozoa: effect of gossypol in vivo (1986)
    Springer
    Urological research 14 (1986), S. 247-252 
    Details
    ISSN: 1434-0879
    Keywords: Monkey spermatozoa ; Gossypol effect ; In vivo examination ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The present study examines the ultrastructure of ejaculated spermatoza from bonnet monkey, Macaca radiata under noraml conditions, with gossypol treatment and during recovery from such treatment. Monkeys were fed orally with gossypol acetic acid (GAA) for 3 months (4 mg/monkey/5 days a weak). Semen samples collected by electroejaculation, and the spermatozoa were examined using both light and electron microscopy. The degree of motility was also noted by Kalla et al. [12]. Ejaculated spermatoza were immotile 90 days after GAA treatment, but little evidence for any abnormality in the spermatozoa could be seen by light microscopy. Some ultrastructural changes were observed, but not to the extent previously reported in spermatozoa of Macaca fascicularis [23]. After termination of treatment, semen samples were obtained every 5th day until sperm count and motility recovered to the normal level. After 90 days only a small proportion of spermatozoa showed abnormal structure. We conclude that in a subhuman animal model gossypol induced effects on sperm motility and morphology are reversible.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00256567
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Work function and barrier heights of transition metal silicides (1986)
    Springer
    Applied physics 40 (1986), S. 71-77 
    Details
    ISSN: 1432-0630
    Keywords: 73.40
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The work function of 13 polycrystalline transition metal suicides was measured by photoemission in uhv. Their values are discussed in relationship to their Schottky barrier heights on n-Si. While there appears to be a weak correlation for a certain group of transition metal suicides, the values of the 5d-noble metal suicides including some of the lattice matched Ni suicides appear to be completely uncorrelated. Experimental values of work functions are compared to the values proposed previously by Freeouf.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00616480
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    DC-potential shifts and regional cerebral blood flow reveal frontal cortex involvement in human visuomotor learning (1988)
    Springer
    Experimental brain research 71 (1988), S. 353-364 
    Details
    ISSN: 1432-1106
    Keywords: Movement ; Movement related potentials ; Cerebral blood flow ; Learning ; Frontal cortex
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In the present study, two different physiological parameters were measured to describe brain activity related to visuomotor learning: performance-related DC-potential shifts and regional cerebral blood flow (rCBF) by Tc-99m HMPAO brain SPECT (Single Photon Emission Computerized Tomography). Visuomotor learning was required in a conflicting situation: a visual target moved on a screen and had to be tracked by moving the right hand in an inverted fashion (IT), e.g. movements of the target to the right side required hand movement to the left and vice versa. Compared to a normal, non-inverted control task (T), IT required the development of a novel motor program and the prevention of returning to routine direct pursuit. These additional demands in IT caused a relative hyperperfusion in regions including the middle frontal gyri, frontomedial cortex (including the supplementary motor area, SMA), right basal ganglia (caudate-putamen) and left cerebellum. Correlations of rCBF values between the middle frontal gyrus and basal ganglia may indicate a functional relation between these two brain structures. Visuomotor performance was accompanied by slow negative DC-potential shifts. In frontal and to a lesser degree in central recordings, amplitudes of DC-negativity were larger in IT than they were in T. This additional frontal negativity covaried with the success of learning. Results substantiate, now using a dual approach, previous suggestions that the frontal lobe plays an important role in visuomotor learning.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00247495
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    67Zn Mössbauer study of Cu−Zn alloys at high pressure (1990)
    Springer
    Hyperfine interactions 54 (1990), S. 759-765 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The high-resolution 93.3-keV Mössbauer resonance in67Zn was used to investigate Cu−Zn alloys (brass) containing 16.6 wt.% Zn (α-phase) and 50.5 wt.% Zn (β'-phase) at pressures up to 6.2 GPa and at 4.2 K. The recoil-free fraction and the center shift change linearly with reduced volume. The decrease of the center shift is due to the second-order Doppler effect which is partially compensated by the increase of the s-electron density at the67Zn nucleus when the conduction electrons are compressed. In α-brass short-range order leads to four different Cu−Zn configurations. One of them exhibits a center shift which nearly coincides with that of the β'-phase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02396125
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Magnetic excitations in the quasi one-dimensional antiferromagnetic singlet groundstate system CsFeBr3 (1988)
    Springer
    The European physical journal 72 (1988), S. 487-496 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We have measured the magnetic excitations in CsFeBr3 along the chain direction (z-axis) and perpendicular to it by inelastic neutron scattering. The measured dispersion curves can be reproduced by the formula $$\omega ^2 (q) = A^2 - 8A[J\cos (\pi q_c ) + J'\gamma (2\pi q_ \bot )]R(T)$$ which is very different from dispersion relations for usual 1 D antiferromagnets, because of the singlet groundstate of this system. The large value of the anisotropy energyA/k=29.8±0.5 K, which is independent of temperature, causes the singlet groundstate. The intra-and inter-chain exchange parameters areJ/k=−3.2±0.15K andJ'/k=−0.32±0.02 K determined atT=1.4 K. At 1.4 K the renormalisation factor is taken to beR(T)=1. AtT=30 K the value forR(T) was found to be 0.5±0.1 keepingJ andJ' unchanged. The excitations at (1/3 1/31) show soft mode behaviour but no phase transition. The observed intensities are interpreted by a heuristic model for the eigenvectors in the excited state including antiferro-as well as ferromagnetic configurations of the fluctuations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01314530
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    Calibration and applications of polarized neutron thermometry at milli- and microkelvin temperatures (1988)
    Springer
    The European physical journal 71 (1988), S. 139-148 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We have utilized the polarized neutron scattering technique for the determination of the nuclear temperature in copper from 20 mK down to 100 μK. Using a cooling facility where two adiabatic demagnetization stages work in series we have calibrated the flipping ratio of neutrons scattered from the (200) Bragg-peak against the nuclear polarization over the whole polarization range. The observed calibration curve deviates considerably from the curve expected for an extinction-free sample. The polarized neutron thermometer is discussed and applied in measurements of the spin-lattice relaxation in copper.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01312783
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...