ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

feed icon rss

Your email was sent successfully. Check your inbox.

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

Proceed reservation?

Export
Filter
  • Articles  (41)
  • Springer  (41)
Collection
  • Articles  (41)
Journal
  • 1
    ISSN: 0992-7689
    Keywords: Ionosphere (auroral ionosphere; plasma convection) ; Magnetospheric physics (storms and substorms)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract On 7 December 1992, a moderate substorm was observed by a variety of satellites and ground-based instruments. Ionospheric flows were monitored near dusk by the Goose Bay HF radar and near midnight by the EISCAT radar. The observed flows are compared here with magnetometer observations by the IMAGE array in Scandinavia and the two Greenland chains, the auroral distribution observed by Freja and the substorm cycle observations by the SABRE radar, the SAMNET magnetometer array and LANL geosynchronous satellites. Data from Galileo Earth-encounter II are used to estimate the IMF Bz component. The data presented show that the substorm onset electrojet at midnight was confined to closed field lines equatorward of the pre-existing convection reversal boundaries observed in the dusk and midnight regions. No evidence of substantial closure of open flux was detected following this substorm onset. Indeed the convection reversal boundary on the duskside continued to expand equatorward after onset due to the continued presence of strong southward IMF, such that growth and expansion phase features were simultaneously present. Clear indications of closure of open flux were not observed until a subsequent substorm intensification 25 min after the initial onset. After this time, the substorm auroral bulge in the nightside hours propagated well poleward of the pre-existing convection reversal boundary, and strong flow perturbations were observed by the Goose Bay radar, indicative of flows driven by reconnection in the tail.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 2
    ISSN: 0992-7689
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract A discussion is given of plasma flows in the dawn and nightside high-latitude ionospheric regions during substorms occurring on a contracted auroral oval, as observed using the EISCAT CP-4-A experiment. Supporting data from the PACE radar, Greenland magnetometer chain, SAMNET magnetometers and geostationary satellites are compared to the EISCAT observations. On 4 October 1989 a weak substorm with initial expansion phase onset signatures at 0030 UT, resulted in the convection reversal boundary observed by EISCAT (at \sim0415 MLT) contracting rapidly poleward, causing a band of elevated ionospheric ion temperatures and a localised plasma density depletion. This polar cap contraction event is shown to be associated with various substorm signatures; Pi2 pulsations at mid-latitudes, magnetic bays in the midnight sector and particle injections at geosynchronous orbit. A similar event was observed on the following day around 0230 UT (\sim0515 MLT) with the unusual and significant difference that two convection reversals were observed, both contracting poleward. We show that this feature is not an ionospheric signature of two active reconnection neutral lines as predicted by the near-Earth neutral model before the plasmoid is “pinched off”, and present two alternative explanations in terms of (1) viscous and lobe circulation cells and (2) polar cap contraction during northward IMF. The voltage associated with the anti-sunward flow between the reversals reaches a maximum of 13 kV during the substorm expansion phase. This suggests it to be associated with the polar cap contraction and caused by the reconnection of open flux in the geomagnetic tail which has mimicked “viscous-like” momentum transfer across the magnetopause.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 3
    ISSN: 1573-4846
    Keywords: II–VI semiconductor ; ultrasounds ; quantum dots ; nanoparticles ; DCCA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract SiO2 gels obtained by sonocatalytic method combined with DCCA were used as host-matrices for extremely fine dispersions of CdS semiconductor particles. Small crystallites were produced “in situ” by H2S gas diffusion method. The particles were characterized by TEM and HRTEM, EXAFS, UV-Vis and Raman spectroscopies. The size of crystallites ranged from 5 to 10 nm. The optical transmission spectra showed the characteristic blue shift as a function of the particles size, as predicted by the theory. The optical and mechanical qualities of the samples were substantially improved by an infiltration method using a sono-sol which sealed the superficial pores thus ensuring greater longevity and the possibility of obtaining transparent gels by polishing.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 4
    ISSN: 1573-4846
    Keywords: CdSe nanocrystals ; silica xerogels ; sonogels ; SAXS
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Small-angle X-ray scattering (SAXS) experiments were carried out to characterize the structure of the composite formed by CdSe nanocrystals embedded in a popous silica matrix (silica xerogels containing Cd with formamide addition and ultrasound treatment). SAXS results from samples before Se diffusion indicate the presence of heterogeneities with a bimodal size distribution which was associated to the existence of mesopores (pores of several hundred Å) immersed in a nanoporous matrix (characteristic pore radii of 20–30 Å). The diffusion of Se induces the nucleation and growth of CdSe nanocrystals. The average size of the nanocrystals increases with Cd content. Higher Se doses promote the formation of larger nanocrystals (radius of gyration of ∼30 to 50 Å). Anomalous scattering results confirm the existence of Se aggregation associated with CdSe nanocrystal formation and suggest that only partial segregation of Cd and Se occurs.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 13 (1998), S. 629-633 
    ISSN: 1573-4846
    Keywords: quantum dots ; II–VI crystal growth ; silica gel ; SANS
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Size and size distribution of the semiconductor nanocrystals embedded in a dielectric matrix play a dominant role in line broadening and the exciton quantum confinement level. The results show new aspects of the CdS and CdSe crystal growth as quantum dots using small angle neutron scattering techniques (SANS). Thus, the crystal growth influences the aggregation process of the silica network. The intensity difference of the scattering between the silica matrix and the composite accounts for the crystal size and their volume fraction. Under similar conditions CdS nanocrystals grow faster and bigger than CdSe ones.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 2 (1994), S. 347-352 
    ISSN: 1573-4846
    Keywords: zirconia ; sintering ; densification ; heat treatment ; yttria stabilized zirconia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Amorphous zirconia ceramics powders containing 3 and 6 mol% yttria were prepared by controlled hydrolysis of alkoxides. Characterization of these powders was carried away by Thermal Analysis, X-ray Diffraction, Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Analysis (EDAX™). The calcination temperature was optimized for compaction at a temperature ranging from 500–800°C. 3% molar YSZ powders from alkoxide, that attained 98% of the theoretical bulk density, showed the best behaviour.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Zeitschrift für angewandte Mathematik und Physik 24 (1973), S. 853-860 
    ISSN: 1420-9039
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Physics
    Description / Table of Contents: Résumé Le but de cet article est de développer une théorie spéciale des fluides à molécules polaires afin d'éclaircir deux questions soulevées dans un récent article de Muller (1), à savoir: le flux de chaleur et une possible relation de dépendance entre la tension et le système de coordonnées choisi.
    Notes: Summary A special theory of polar fluids is developed with a view to providing some insight into the questions of the frame-dependence of stress and heat flux, arising out of a recent paper by Müller (1).
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Zeitschrift für angewandte Mathematik und Physik 28 (1977), S. 1017-1026 
    ISSN: 1420-9039
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Physics
    Description / Table of Contents: Zusammenfassung Es werden einige Einschränkungen für die Randbedingungen in der Kontinuumsmechanik behandelt, die von der Forderung herrühren, dass für die Materie ausserhalb der Grenzfläche die fundamentalen Bilanzgleichungen, die Invarianzbedingungen und die Entropieungleichung gelten sollen. Diese Behauptungen werden für polare Materialien erläutert, jedoch sind die hier eingeführten Begriffe auf Kontinuumstheorien aller Art anwendbar.
    Notes: Summary We discuss some restrictions on boundary conditions in continuum mechanics arising from the requirement that the basic balance laws, invariance conditions and entropy inequality must hold for the material outside of the bounding surface. We illustrate our assertions for polar materials, but the ideas we use are applicable to all continuum theories.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Rheologica acta 16 (1977), S. 213-222 
    ISSN: 1435-1528
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Zusammenfassung Das Isotop Helium 4 unter 2,2°K, bekannt als Helium II, zeigt einige merkwürdige mechanische und thermische makroskopische Effekte. In dieser Arbeit wird eine mögliche Alternative zu der Zweiflüssigkeitentheorie für Helium II besprochen. Standardmethoden der Kontinuumsmechanik werden benutzt, um den Fluß gewisser mikroskopischer Anregungszustände zu beschreiben, die als Ursache der beobachteten Effekte angesehen werden. Passende Bilanzgleichungen werden aufgestellt und Stoffgleichungen vorgeschlagen. Einige einfache Lösungen der sich ergebenden Theorie werden diskutiert, die qualitative Übereinstimmung mit den beobachteten Effekten liefern. Diese Effekte betreffen das Experiment der hängenden Platte von Hall, den Springbrunneneffekt und Schall-Wellen zweiter Art bei kleinen Amplituden.
    Notes: Summary The isotope helium 4 below 2.2°K, known as helium II, exhibits a number of curious mechanical and thermal macroscopic effects. In this paper a possible alternative to the two-fluid theory for helium II is reviewed. Standard techniques of continuum mechanics are used to describe the flow of certain microscopic excitations which are believed to give rise to the observed effects. Appropriate balance laws are formulated and constitutive equations are proposed. Some simple solutions of the resulting theory are discussed which give qualitative agreement with observed effects. These effects include Hall's hanging plate experiment, the fountain effect and smallamplitude second-sound waves.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Archive for rational mechanics and analysis 87 (1984), S. 1-9 
    ISSN: 1432-0673
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Physics
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...