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
  • 11
    Electronic Resource
    Electronic Resource
    Permittivity and Permeability of Mullite-SiC-Whisker and Spinel-SiC-Whisker Composites (1998)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 81 (1998), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Real and imaginary permittivity (ɛ′ and ɛ″, respectively) values were determined on mullite-silicon carbide whisker (mullite-SiCw) composites, mullite-ZrO2 composites, and spinel-SiCw composites, in the frequency range of 2-18 GHz, using a 14 mm coaxial air-line measurement system. Depending on the frequency, the addition of 30 vol% of SiCw to mullite increases ɛ′ from 6.6-6.9 to 16-22 and increases ɛ′ from 0 to 16-22. The addition of 32 vol% of SiCw to spinel increases ɛ′ from 7.5-7.8 to 37-44 and increases ɛ″ from 0 to 13-20. The addition of 21 vol% of ZrO2 to mullite increases ɛ″ to ∼9 but does not change ɛ″. Real and imaginary permeability values were 1 and 0, which are within experimental error.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1998.tb02452.x
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 12
    Electronic Resource
    Electronic Resource
    Systemic Administration of NMDA and AMPA Receptor Antagonists Reverses the Neurochemical Changes Induced by Nigrostriatal Denervation in Basal Ganglia (1999)
    Oxford UK : Blackwell Science Ltd
    Journal of neurochemistry 73 (1999), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: In Parkinson’s disease, nigrostriatal denervation leads to an overactivity of the subthalamic nucleus and its target areas, which is responsible of the clinical manifestations of the disease. Because the subthalamic nucleus uses glutamate as neurotransmitter and is innervated by glutamatergic fibers, pharmacological blockade of glutamate transmission might be expected to restore the cascade of neurochemical changes induced by a dopaminergic denervation within the basal ganglia. To test this hypothesis, two types of glutamate antagonists, the NMDA receptor antagonist MK-801 and the α-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA) receptor antagonist LY293558, were administered systemically, either alone or in combination with L-DOPA, in rats with a unilateral 6-hydroxydopamine lesion of the nigrostriatal dopamine pathway. The effect of treatment was assessed neurochemically by analyzing at the cellular level the functional activity of basal ganglia output structures and the subthalamic nucleus using the expression levels of the mRNAs coding for glutamic acid decarboxylase and cytochrome oxidase, respectively, as molecular markers of neuronal activity. The present study shows that treatment with glutamate antagonists, and particularly with AMPA antagonists, alone or in combination with L-DOPA, reverses the overactivity of the subthalamic nucleus and its target areas induced by nigrostriatal denervation. These results furnish the neurochemical basis for the potential use of glutamate antagonists as therapeutic agents in Parkinson’s disease.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1471-4159.1999.0730344.x
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 13
    Electronic Resource
    Electronic Resource
    LUXEMBOURG (1996)
    Oxford, UK : Blackwell Publishing Ltd
    European journal of political research 30 (1996), S. 0 
    Details
    ISSN: 1475-6765
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Political Science
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1475-6765.1996.tb00694.x
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 14
    Electronic Resource
    Electronic Resource
    Striatal Expression of Glutamic Acid Decarboxylase Gene in Alzheimer's Disease (1998)
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 71 (1998), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: To examine potential alteration of GABAergic striatal neurons in Alzheimer's disease, we used quantitative in situ hybridization to analyze the messenger RNA coding for Mr 67,000 glutamic acid decarboxylase (GAD67 mRNA) in the striatum of five patients with Alzheimer's disease (AD) and nine matched control subjects. We found a 51–57% increase in the optical density of hybridization signal in the caudate nucleus and putamen, corresponding to a 30–42% increase in the number of neurons expressing a detectable amount of GAD67 mRNA. By contrast, no alteration was observed in the ventral striatum. The expression of GAD67 mRNA per neuron was similar in AD and control subjects both in the dorsal and ventral striatum. Taken together, our data indicate that, in AD, GABAergic neurotransmission is increased in the dorsal striatum but not in the ventral striatum. We suggest that this increased GABAergic neurotransmission may explain extrapyramidal signs often observed in AD.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1471-4159.1998.71020767.x
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 15
    Electronic Resource
    Electronic Resource
    Is Differential Regulation of Mitochondrial Transcripts in Parkinson's Disease Related to Apoptosis? (1997)
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 68 (1997), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: A cDNA library of substantia nigra pars compacta from a patient with Parkinson's disease (PD) was differentially screened with probes of normal and parkinsonian substantia nigra enriched in neuronal transcripts. Fifty-eight clones were isolated; 39 were subunits of mitochondrial respiratory complexes I and IV. Parallel screening of a cDNA library derived from normal substantia nigra confirmed differential representation of the transcripts in the substantia nigra pars compacta. In situ hybridization in postmortem brain from parkinsonian and control subjects, with representative complex I and complex IV probes, showed increased labeling, at the cellular level, of the complex I subunit ND1 in neurons of the lateral substantia nigra, where cell death is greatest in PD, but decreased labeling in the medial substantia nigra where fewer cells die. Expression of a complex IV subunit, COXI, increased, however, in both parts of the structure. Increased expression of ND1 and COXI was also observed in nerve growth factor-differentiated PC12 cells undergoing apoptosis induced by tumor necrosis factor-α, suggesting that the differential regulation of certain mitochondrial mRNAs may be associated with this form of cell death. This in vitro model of apoptosis is potentially relevant to the death of dopaminergic neurons in PD, because these cells express the tumor necrosis factor-α receptor, and neighboring microglial cells in patients synthesize the cytokine.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1471-4159.1997.68052098.x
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 16
    Electronic Resource
    Electronic Resource
    LUXEMBOURG (1995)
    Oxford, UK : Blackwell Publishing Ltd
    European journal of political research 28 (1995), S. 0 
    Details
    ISSN: 1475-6765
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Political Science
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1475-6765.1995.tb00507.x
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 17
    Electronic Resource
    Electronic Resource
    An infrared absorption investigation of hydrogen, deuterium, and nitrogen in ZnSe grown by molecular beam epitaxy (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 6425-6428 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Surprising concentrations of hydrogen and deuterium, as high as 5×1020 cm−3, were incorporated into nitrogen-doped ZnSe grown on GaAs by molecular beam epitaxy. Infrared absorption bands due to local vibration modes were observed at 3193 and 783 cm−1 for ZnSe:N,H samples, and at 2368 cm−1 for ZnSe:N,D samples using Fourier transform infrared spectroscopy. The isotopic shift in the absorption band agrees with predictions of a simple harmonic oscillator approximation for N–H bonding. The variation of the absorption band associated with substitutional nitrogen with nitrogen concentration indicates that not all nitrogen is substitutional, and also exhibited significant changes related to hydrogen incorporation. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363661
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 18
    Electronic Resource
    Electronic Resource
    Luminescent Sr1−xErxF2+x thin films grown on InP(100) substrates. II. Optical properties (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 5388-5393 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Photoluminescence and cathodoluminescence studies, performed at room temperature, on Sr1−xErxF2+x/InP(100) layers exhibit strong light emissions in both the visible range and in the infrared domain. It is shown that in the visible range the highest intensities were found for x=0.02, while for the 4I13/2→4I15/2 infrared emission (1.53 μm) the maximum of luminescence was found for x close to 0.2. For a 4I15/2→4I11/2 (980 nm) excitation, up conversion leads to visible light emissions (red and green). A photoluminescence study at low temperature (2 K) shows that, due to the low growth temperature of the layers, the Er3+ environment is more simple than in bulk crystals. For x=0.03 a single charge compensated Er3+ ion site was evidenced. Up to x=0,15 this site predominates but a clustering process is evidenced. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359228
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 19
    Electronic Resource
    Electronic Resource
    Low temperature luminescence studies of Ca1−xErxF2+x thin films epitaxially grown on silicon substrates (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 494-498 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Room temperature photoluminescence studies of Ca1−xErxF2+x thin films epitaxially grown on silicon substrates exhibit strong light emissions in both the visible range and the infrared domain. With an Ar+-ion laser as an excitation source, the maximum of the 4I13/2→4I15/2 infrared (1530 nm) luminescence of Er3+ (4f11) ions was found for x=0.16. It is assumed that a particular Er3+ ion environment exists in the layers to explain why the quenching phenomena do not dominate at these very high erbium concentrations. To describe this environment, a photoluminescence study at low temperature (2 K) has been performed which shows that only one Er3+ ion site (having C4v symmetry) predominates for an erbium substitution rate x≤0.02. At higher Er3+ concentrations, however, a clustering process of erbium ions is observed. In thin films, however the clustering appears only at concentrations two orders of magnitude higher than in bulk single cystals. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.362753
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 20
    Electronic Resource
    Electronic Resource
    Visible photoluminescence from porous a-Si:H and porous a-Si:C:H thin films (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 82 (1997), S. 1832-1840 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report on the influence of doping, temperature, porosity, band gap, and oxidation on the photoluminescence (PL) properties of anodically etched porous a-Si:H and a-Si:C:H thin films. Only boron-doped, p-type a-Si:H samples exhibited visible photoluminescence. Two broad PL peaks at ∼1.6 and ∼2.2 eV are apparent in room temperature PL spectra. The intensity of the 2.2 eV peak as well as the nanovoid density in the unetched a-Si:H layers both correlate well with boron concentration. We see evidence of discrete defect or impurity levels in temperature-dependent luminescence measurements, where we observe multiple luminescence peaks. Unlike in porous crystalline silicon, the luminescence energy in porous amorphous silicon does not change with porosity. We do, though, observe a correlation of luminescence energy with band gap of the starting a-Si:C:H films. Oxidation, either native or anodic, reduces photoluminescence intensity. We discuss the implications of these observations on the nature of the luminescence mechanism. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.365986
    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...