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  • 1995-1999  (99)
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  • 1
    Electronic Resource
    Electronic Resource
    ApoE2 Allele, Down's Syndrome, and Dementia (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 777 (1996), S. 0 
    Details
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Notes: All individuals with Down's syndrome (trisomy 21-DS) develop the pathogenic hallmarks of Alzheimer's disease in old age (+40 years).1-4 The extent of pathology is variable, but it has been shown that the amount of β-amyloid pathology is variable and related to age and the degree of dementia.3 Thus, in DS, growing old is associated with a progressive pathological process which results in cognitive decline. However, neuropsychological studies of older DS subjects have identified a clinical dementia in only a proportion of cases.1-4These contradictory observations could be reconciled if some factor existed which modulated the rate and amount of β-amyloid pathology. Recent studies demonstrate an association between the apolipoprotein E4 (ApoE4) allele and the earlier age of onset in both sporadic8-9 and familial10 AD. Increased amounts of βamyloid pathology can also be related to the E4 allele. However, at present there are no data documenting the effects of ApoE genotype on the expression or degree of clinical symptoms of the disease. We have examined the ApoE genotype in a cohort of clinically evaluated elderly patients with DS in order to examine the effects of ApoE genotype on the clinical symptoms of dementia. We report here that, despite the presence of an active disease process, the ApoE E2 allele is associated with longevity and preservation of cognitive functioning.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1749-6632.1996.tb34428.x
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  • 2
    Electronic Resource
    Electronic Resource
    Prescribing oral contraceptives (1996)
    [s.l.] : Nature Publishing Group
    Nature 379 (1996), S. 764-764 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] SIR - Michael Rawlins1 draws attention to errors in your leading article2 on the latest UK 'pill scare'. But one error, which he does not mention, acquires fresh relevance with the publication of interim data from the study of cardiovascular disease in oral contraceptive (OC) users directed by ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/379764b0
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  • 3
    Electronic Resource
    Electronic Resource
    Deep-oxide planar buried-channel AlGaAs–GaAs quantum well heterostructure waveguides with low bend loss (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 66 (1995), S. 1912-1914 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Data are presented on planar S-bend waveguides fabricated in an AlxGa1−xAs–GaAs p-n quantum well heterostructure (QWH) crystal by a self-aligned process combining Si impurity-induced layer disordering and "wet'' native oxidation. In the process, a deep, low-index (n∼1.7) oxide cladding structure is formed, creating a buried channel in the QWH core layers and defining the routing properties of ∼2.5-μm-wide guides. Deep-oxide S-bend waveguides with 100 μm offsets exhibit low excess bend losses with a 3 dB transition distance less than 140 μm for transverse electric polarization. These bend losses are significantly lower than those measured for oxide-only and disordered-only guides. Excellent optical isolation of the guided signal is observed, indicating very little crosstalk occurs between adjacent guides. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.113319
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  • 4
    Electronic Resource
    Electronic Resource
    Calculated electronic structure of GaAs/Ge2 (001) superlattices (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 758-764 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We use the semiempirical tight binding method with an sp3s* basis and second-nearest-neighbor interactions to investigate the electronic structure of (GaAs)m/(Ge2)n (001) superlattices (SLs) with 1≤(m,n)≤20. We have found no correspondence between the calculated band structures of these (GaAs)/(Ge2) SLs and those for (GaAs)1−x(Ge2)x random alloys. The inclusion of second-nearest-neighbor, compared with the nearest-neighbor interactions, raised the SL band gap for (m,n)〉1, while lowering that for m=n=1. For the (GaAs)20/(Ge2)20 (001) SLs our calculation gives a band gap energy of 0.79 eV, while for (GaAs)1/(Ge2)1 the band gap energy is 0.11 eV. For small values of m, the (GaAs)m/(Ge2)n SLs are predicted to have indirect band gaps regardless of the valence band offset used in the calculation. For larger values of m, however, the predicted SL band gaps become direct for large values of valence band offset. For ΔEv=0.85 eV we find a direct to indirect band gap transition for m between 14 and 16. In the indirect-gap SLs, the electrons and holes are confined in the Ge layers, while the direct-gap SLs have holes confined in the Ge layers and electrons in the GaAs layers. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.364137
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  • 5
    Electronic Resource
    Electronic Resource
    Electronic structure of (GaAs)m/(Ge2)n (001) superlattices with 1≤(m,n)≤20 (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 1942-1944 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The semiempirical tight-binding method with second-nearest-neighbor interactions has been used to investigate the electronic structure of (GaAs)m/(Ge2)n (001) superlattices (SLs) with 1≤(m,n)≤20. We have found no correspondence between the calculated band structures of these (GaAs)/(Ge2) SLs and (GaAs)1−x(Ge2)x random alloys. The inclusion of second-nearest-neighbor interactions raised the predicted energies of the conduction band confined states while lowering that of the highest-lying interface state. For small values of m, the (GaAs)m/(Ge2)n SLs are predicted to have indirect band gaps regardless of the valence band offset used in the calculation. For larger values of m, however, the predicted SL band gaps become direct for large values of valence band offset. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.115633
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  • 6
    Electronic Resource
    Electronic Resource
    Temperature and oxygen tension influence the development of muscle cellularity in embryonic rainbow trout (1998)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 53 (1998), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Muscle cellularity at a developmental stage around the time of hatching was examined in rainbow trout which had been reared from the eyed stage at three different temperature regimes (5, 10 and 15° C) and different O2 tensions [70% of air saturation value (ASV) at 5° C, 100% of ASV at all temperatures, and 150% of ASV at 10 and 15° C]. It was found that, as has been shown for other species, there was a difference in muscle fibre numbers and fibre cross-sectional areas between some of the regimes. There was a decrease in fibre number at the intermediate and higher temperature, and a decrease in fibre size at the high temperature. The temperature effects observed were modified by the applied changes in O2 tension. An increased O2 tension at 10° C led to an increase in fibre size whereas a decrease in O2 tension at the low temperature resulted in a decrease in fibre number. The largest total white muscle cross-sectional area was achieved at 10° C under high O2 conditions. Temperature and O2 tension therefore had a clear effect on muscle cellularity and there was a significant interaction between the two parameters.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1095-8649.1998.tb01003.x
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  • 7
    Electronic Resource
    Electronic Resource
    α-2 macroglobulin gene and Alzheimer disease (1999)
    [s.l.] : Nature America Inc.
    Nature genetics 22 (1999), S. 17-19 
    Details
    ISSN: 1546-1718
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Medicine
    Notes: [Auszug] Blacker et al. reported an association between a deletion in exon 18 of the α-2 macroglobulin (A2M) gene and Alzheimer disease (AD) in a sample of affected and unaffected siblings from families segregating AD. They observed that the degree of conferred risk for AD in A2M allele 2 (A2M*2) ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/8726
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  • 8
    Electronic Resource
    Electronic Resource
    The Role of Axonal Delay in the Synchronization of Networks of Coupled Cortical Oscillators (1997)
    Springer
    Journal of computational neuroscience 4 (1997), S. 161-172 
    Details
    ISSN: 1573-6873
    Keywords: axonal delay ; cortical oscillators ; phase ; synchrony ; coupled oscillators
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Medicine , Physics
    Notes: Abstract Coupled oscillator models use a single phase variable to approximate the voltage oscillation of each neuron during repetitivefiring where the behavior of the model depends on the connectivityand the interaction function chosen to describe the coupling. Weintroduce a network model consisting of a continuum of theseoscillators that includes the effects of spatially decaying coupling and axonal delay. We derive equations for determining the stability of solutions and analyze the network behavior for two different interaction functions. The first is a sine function, and the second is derived from a compartmental model of a pyramidal cell.In both cases, the system of coupled neural oscillators can undergo a bifurcation from synchronous oscillations to waves.The change in qualitative behavior is due to the axonal delay,which causes distant connections to encourage a phase shift between cells. We suggest that this mechanism could contribute to the behavior observed in several neurobiological systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008843412952
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  • 9
    Electronic Resource
    Electronic Resource
    Dendritic and Synaptic Effects in Systems of Coupled Cortical Oscillators (1998)
    Springer
    Journal of computational neuroscience 5 (1998), S. 315-329 
    Details
    ISSN: 1573-6873
    Keywords: synchrony ; cortical oscillators ; phase model ; synaptic effects ; dendritic delay
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Medicine , Physics
    Notes: Abstract We explore the influence of synaptic location and form on the behavior of networks of coupled cortical oscillators. First, we develop a model of two coupled somatic oscillators that includes passive dendritic cables. Using a phase model approach, we show that the synchronous solution can change from a stable solution to an unstable one as the cable lengthens and the synaptic position moves further from the soma. We confirm this prediction using a system of coupled compartmental models. We also demonstrate that when the synchronous solution becomes unstable, a bifurcation occurs and a pair of asynchronous stable solutions appear, causing a phase lag between the cells in the system. Then using a variety of coupling functions and different synaptic positions, we show that distal connections and broad synaptic time courses encourage phase lags that can be reduced, eliminated, or enhanced by the presence of active currents in the dendrite. This mechanism may appear in neural systems where proximal connections could be used to encourage synchrony, and distal connections and broad synaptic time courses could be used to produce phase lags that can be modulated by active currents.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008839112707
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  • 10
    Electronic Resource
    Electronic Resource
    Alzheimer disease PS-1 exon 9 deletion defined (1999)
    [s.l.] : Nature America Inc.
    Nature medicine 5 (1999), S. 1090-1090 
    Details
    ISSN: 1546-170X
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Medicine
    Notes: [Auszug] To the editor—The clinical, pathological, and genetic analyses of a Finnish pedigree (Finn2) with early-onset inherited Alzheimer disease (AD) have been reported. This family demonstrated linkage to the PS1 region of chromosome 14, and analysis for PS1 mutations by RT–PCR and ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/13383
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