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  • 1
    Electronic Resource
    Electronic Resource
    Effect of negative gain suppression on the stability of laser diodes (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 66 (1995), S. 1874-1876 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The stability of homogeneously pumped single-section laser diodes is analyzed theoretically and it is found that under certain bias conditions negative gain suppression factor laser diodes (NGSFLDs) self-pulsate. An analytical condition for self-pulsation in homogeneously pumped single-section laser diodes is derived. The dynamics of self-pulsating NGSFLDs under direct modulation are analyzed and a quasiperiodic route to chaos is found. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.113306
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  • 2
    Electronic Resource
    Electronic Resource
    Mean flow and turbulence structure over fixed, two-dimensional dunes: implications for sediment transport and bedform stability (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Sedimentology 42 (1995), S. 0 
    Details
    ISSN: 1365-3091
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Detailed measurements of flow velocity and its turbulent fluctuation were obtained over fixed, two-dimensional dunes in a laboratory channel. Laser Doppler anemometry was used to measure the downstream and vertical components of velocity at more than 1800 points over one dune wavelength. The density of the sampling grid allowed construction of a unique set of contour maps for all mean flow and turbulence parameters, which are assessed using higher moment measures and quadrant analysis. These flow field maps illustrate that: (1) the time-averaged downstream and vertical velocities agree well with previous studies of quasi-equilibrium flow over fixed and mobile bedforms and show a remarkable symmetry from crest to crest; (2) the maximum root-mean-square (RMS) of the downstream velocity values occur at and just downstream of flow reattachment and within the flow separation cell; (3) the maximum vertical RMS values occur within and above the zone of flow separation along the shear layer and this zone advects and diffuses downstream, extending almost to the next crest; (4) positive downstream skewness values occur within the separation cell, whereas positive vertical skewness values are restricted to the shear layer; (5) the highest Reynolds stresses are located within the zone of flow separation and along the shear layer; (6) high-magnitude, high-frequency quadrant-2 events (‘ejections’) are concentrated along the shear layer (Kelvin-Helmholtz instabilities) and dominate the contribution to the local Reynolds stress; and (7) high-magnitude, high-frequency quadrant-4 events occur bounding the separation zone, near reattachment and close to the dune crest, and are significant contributors to the local Reynolds stress at each location. These data demonstrate that the turbulence structure associated with dunes is controlled intrinsically by the formation, magnitude and downstream extent of the flow separation zone and resultant shear layer. Furthermore, the origin of dune-related macroturbulence lies in the dynamics of the shear layer rather than classical turbulent boundary layer bursting. The fluid dynamic distinction between dunes and ripples is reasoned to be linked to the velocity differential across the shear layer and hence the magnitude of the Kelvin-Helmholtz instabilities, which are both greater for dunes than ripples. These instabilities control the local flow and turbulence structure and dictate the modes of sediment entrainment and their transport rates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3091.1995.tb00386.x
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  • 3
    Electronic Resource
    Electronic Resource
    Periodic acid-Schiff(PAS)-positive deposits in brain following kainic acid-induced seizures: relationships to fos induction, neuronal necrosis, reactive gliosis, and blood-brain barrier breakdown (1995)
    Springer
    Acta neuropathologica 89 (1995), S. 126-138 
    Details
    ISSN: 1432-0533
    Keywords: Neurodegeneration ; Epilepsy ; Kainic acid fos ; Gliosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Periodic acid-Schiff (PAS)-positive deposits have been demonstrated in the central nervous system (CNS) of patients suffering from a wide variety of neurodegenerative disorders including Alzheimer's disease, presenile dementia, Parkinson's disease, diabetes mellitus, myoclonic epilepsy, and cerebral palsy. The etiology of these deposits and their relationship to mechanisms of progressive neurodegeneration is unknown. In the present study, we demonstrate that the kainic acid model of limbic status epilepticus provides a useful system for the study of PAS-positive staining. The relationship between PAS-positive deposition, induction of fos-like immunoreactivity (FLI), neuronal necrosis, reactive gliosis, and blood-brain barrier breakdown following the kainic acid induction of status epilepticus was investigated. Epileptiform activity was elicited in rats by intraperitoneal administration of 10 mg/kg kainic acid and brains were examined 3, 5, 12, 24, 72, and 168 h after drug injection. Four distinct types of PAS-positive staining in rat brain were observed: type 1, extracellular matrix (ECM) or blood vessel associated-material; type 2, granular deposits; type 3, glial labelling; and type 4, neuronal labelling. Results demonstrated that the four types of PAS-positive staining were differentially associated with specific markers of neuropathology: (1) type 1 ECM staining and type 3 glia were preferentially localized to edematous tissue; (2) the majority of type 3 glia were identified as reactive astrocytes, while a minority of appeared to be proliferating microglia; (3) type 1 blood vessels labelled hemorrhaging vasculature; (4) early deposition of type 2 granules was predictive of subsequent cell loss; (5) chronic type 2 granular deposits and type 4 neuronal labelling not associated with cell death could be predicted by early changes in FLI; and (6) chronic deposition of all four forms of PAS-positive material was correlated with earlier, transient blood-brain barrier compromise. The results support the growing literature that local carbohydrate metabolism may be one of a constellation of parameters important to the development of progressive neurodegeneration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00296356
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  • 4
    Electronic Resource
    Electronic Resource
    Periodic acid-Schiff(PAS)-positive deposits in brain following kainic acid-induced seizures: relationships to fos induction, neuronal necrosis, reactive gliosis, and blood-brain barrier breakdown (1995)
    Springer
    Acta neuropathologica 89 (1995), S. 126-138 
    Details
    ISSN: 1432-0533
    Keywords: Key words Neurodegeneration ; Epilepsy ; Kainic acid ; fos ; Gliosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Periodic acid-Schiff (PAS)-positive deposits have been demonstrated in the central nervous system (CNS) of patients suffering from a wide variety of neurodegenerative disorders including Alzheimer's disease, presenile dementia, Parkinson's disease, diabetes mellitus, myoclonic epilepsy, and cerebral palsy. The etiology of these deposits and their relationship to mechanisms of progressive neurodegeneration is unknown. In the present study, we demonstrate that the kainic acid model of limbic status epilepticus provides a useful system for the study of PAS-positive staining. The relationship between PAS-positive deposition, induction of fos-like immunoreactivity (FLI), neuronal necrosis, reactive gliosis, and blood-brain barrier breakdown following the kainic acid induction of status epilepticus was investigated. Epileptiform activity was elicited in rats by intraperitoneal administration of 10 mg/kg kainic acid and brains were examined 3, 5, 12, 24, 72, and 168 h after drug injection. Four distinct types of PAS-positive staining in rat brain were observed: type 1, extracellular matrix (ECM) or blood vessel associated-material; type 2, granular deposits; type 3, glial labelling; and type 4, neuronal labelling. Results demonstrated that the four types of PAS-positive staining were differentially associated with specific markers of neuropathology: (1) type 1 ECM staining and type 3 glia were preferentially localized to edematous tissue; (2) the majority of type 3 glia were identified as reactive astrocytes, while a minority of appeared to be proliferating microglia; (3) type 1 blood vessels labelled hemorrhaging vasculature; (4) early deposition of type 2 granules was predictive of subsequent cell loss; (5) chronic type 2 granular deposits and type 4 neuronal labelling not associated with cell death could be predicted by early changes in FLI; and (6) chronic deposition of all four forms of PAS-positive material was correlated with earlier, transient blood-brain barrier compromise. The results support the growing literature that local carbohydrate metabolism may be one of a constellation of parameters important to the development of progressive neurodegeneration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00296356
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  • 5
    Electronic Resource
    Electronic Resource
    Chromosome identification and mapping in the grassZingeria biebersteiniana (2n=4) using fluorochromes (1995)
    Springer
    Chromosome research 3 (1995), S. 101-108 
    Details
    ISSN: 1573-6849
    Keywords: FISH ; fluorochrome banding ; low chromosome number ; ribosomal RNA genes ; Zingeria biebersteiniana (2n=4)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The grassZingeria biebersteiniana is one of five angiosperms known with 2n=2x=4. Its chromosomes were studied using fluorochrome banding and fluorescencein situ hybridization (FISH). The large pericentromeric region fluoresced much more brightly on chromosome 2 than on chromosome 1, using two different fluorochrome banding methods. These offer rapid and reliable means for identifying chromosomes and work throughout mitosis. FISH located the major site of 18S–26S rDNA sequences at the secondary constriction, which is proximal to two minor sites, all on the short arm of chromosome 1. Two 5S sites were also detected, the most distinct on the short arm of chromosome 2 and the other apparently co-localized with part of the major 18S–26S rDNA cluster on chromosome 1. These results constitute the first steps in constructing a physical gene map forZ. biebersteiniana. Such information may facilitate future studies of the organization and reorganization of grass genomes, including research into the spatial arrangement of the genome inZingeria nuclei and much wider comparisons of synteny and genome evolution in grasses.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00710670
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  • 6
    Electronic Resource
    Electronic Resource
    Lifetime egg production and egg mortality in the damselflyPyrrhosoma nymphula (Sulzer) (Zygoptera: Coenagrionidae) (1995)
    Springer
    Hydrobiologia 310 (1995), S. 71-78 
    Details
    ISSN: 1573-5117
    Keywords: Pyrrhosoma ; egg production ; egg mortality ; lifetime reproductive success
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Artificial oviposition sites were used to estimate egg deposition rates in the field. Females laid an average of 10.76 eggs/minute with a mean duration of 22.81 minutes, giving an average clutch size of 245 eggs. Since one mating corresponded to one clutch of eggs, lifetime mating success was used as a measure of the number of clutches produced. Mean lifetime clutch production was 5.91 clutches per female, equating to 1447 eggs per female per lifetime. Eggs were hatched in the laboratory at temperatures comparable with those in the field. Hatching was highly synchronised and the overall hatching success was 75.1%. Causes of egg mortality in the laboratory were limited to infertility and unhatchability. Since no other sources of egg mortality could be found at the study site, this value was a good reflection of hatching success in the field. Lifetime egg production and hatching success were used to estimate the number of viable offspring produced per female, giving a higher order estimate of reproductive success than has previously been published for a zygopteran.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00008184
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