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  • 1
    Electronic Resource
    Electronic Resource
    Laser etched gratings on polymer layers for alignment of liquid crystals (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 72 (1998), S. 2078-2080 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Liquid crystal alignment layers are prepared using a noncontact method based on laser ablation. Nonpolarized light from a KrF excimer laser at 248 nm is exposed through a phase mask to etch gratings of period 1.1 μm onto polyimide alignment layers. Twisted nematic cells were prepared using one rubbed and one grating aligned surface, and azimuthal anchoring energies were found from measurements of the twist angles as a function of grating depth. The measured anchoring energies agree with those predicted from the minimization of elastic strain energy when the liquid crystal directors at the surface are aligned parallel to the groove of the grating. This suggests that topographical rather than epitaxial alignment is achieved. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.121281
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  • 2
    Electronic Resource
    Electronic Resource
    Anderson localization and Monte Carlo simulation of vertical transport in disordered finite superlattices (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 82 (1997), S. 4378-4383 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effects on the carrier wave functions of introducing monolayer disorder at the heterojunction interfaces of an undoped superlattice are elucidated. In particular the rate and extent of the resulting localization is quantified by means of an entity C, which is the joint probability of finding two carriers in the same region of space. Evaluating the latter for all states in the miniband provides clear evidence for the existence of a mobility edge in finite two-dimensional structures. Using the entity C as the basis for a semiclassical evaluation of carrier transport, it is shown that the experimentally observed activated transport can be accounted for in terms of the excitation of carriers from the localized states at the bottom of the miniband into the more extended midband miniband states. Comparison of the theoretical results with the experimental results given [Chen et al., J. Cryst. Growth 159, 1066 (1996)], enables conclusions to be drawn concerning the mechanism of activated carrier transport in doped superlattice systems. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.366248
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  • 3
    Electronic Resource
    Electronic Resource
    Spectroscopic evidence for different laser gain mechanisms in optically pumped ZnCdS/ZnS quantum well structures (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 84 (1998), S. 5621-5625 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The role of biexcitons has been studied in two optically pumped quantum well (QW) structures of Zn1−xCdxS/ZnS, one with 18% Cd concentration and the other with 3% in the wells. For the x=18% QW structure, high excitation photoluminescence and stimulated emission indicate that the laser gain mechanism involves biexcitons. For the x=3% QWs, even though biexcitons are clearly observed in the spontaneous emission, they are not responsible for laser gain in this structure. Instead exciton–exciton scattering may be the more likely mechanism responsible for laser gain close to threshold, while at higher densities an estimate of the carrier density indicates an electron–hole plasma as the likely source of optical gain. The different mechanisms in the two cases can, very likely, be attributed to one of differing degrees of localization both within the QW and at alloy fluctuations. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.368609
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  • 4
    Electronic Resource
    Electronic Resource
    Emission studies of Ba-hexaferrite plume produced by a KrF excimer laser : The 7th joint MMM-intermag conference on magnetism and magnetic materials (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 6858-6860 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Optical emission measurements and intensified charge coupled detector images of a plasma generated by the interaction of a KrF excimer laser with a Ba-ferrite target have been used to study the laser ablation deposition of Ba ferrite thin films. Time integrated spectra were collected as a function of distance above the target surface and as a function of oxygen pressure. Temporal profiles showed that close to the target the plume is insensitive to ambient oxygen pressure and at greater distances a much more pronounced influence is observed. Time resolved images of the overall optical plasma emission clearly demonstrated how the presence of oxygen confines the plasma and enhances its emission. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.367657
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  • 5
    Electronic Resource
    Electronic Resource
    Spectroscopic evidence for the excitonic lasing mechanism in ultraviolet ZnS/ZnCdS multiple quantum well lasers (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 4230-4232 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We demonstrate optically pumped lasing at room temperature from ZnS/ZnCdS quantum-well structures grown on (100) GaP substrates by molecular beam epitaxy. In the structures with the lowest Cd composition, optically pumped lasing at wavelengths as low as 333 nm (at 8 K) is observed. We present spectroscopic evidence which suggests that the stimulated emission involves states in the low-energy tail of an inhomogeneously broadened excitonic resonance. While lasing is excitonic at low thresholds, a transition to an electron-hole plasma mechanism may occur if the pump power approaches 100 kW cm−2. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.116954
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  • 6
    Electronic Resource
    Electronic Resource
    Whatever happened to SRY? (1999)
    Springer
    Cellular and molecular life sciences 56 (1999), S. 883-893 
    Details
    ISSN: 1420-9071
    Keywords: Key words.SRY; sex determination; SOX; HMG box; Y chromosome; rapid sequence evolution.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. The mammalian sex-determining gene, SRY, was identified by positional cloning approximately 10 years ago. Since its discovery, intense research into this gene has been directed on two main fronts: elucidation of its function in development of the testis and examination of its singular evolutionary history. The role or SRY as the testis-determining factor (TDF) places it at a crucial point in the highly conserved morphogenetic process of vertebrate gonadogenesis. None of the genes that directly activate SRY nor any of its immediate downstream targets have yet been positively identified. Several genes, however, such as SF1, DAX1, and SOX9, whose spatial and temporal expression profiles overlap with that of SRY, are strongly implicated as co-regulators of gonadogenesis. Molecular genetic manipulation of these genes in mice has shown that they are indispensable to sexual development. Remarkably, its key position in this cascade of gene action has not protected SRY from strong yet poorly understood selective forces that have caused it to evolve rapidly in mammals. The evolution of SRY has been characterized not only by rapid sequence divergence within mammals, but also by structural changes such as intron insertion, gene amplification, and deletion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s000180050481
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  • 7
    Electronic Resource
    Electronic Resource
    Acute presentation of cystic adenomatoid malformation of the lung in a 9-year-old child (1995)
    Springer
    Pediatric radiology 25 (1995), S. 572-573 
    Details
    ISSN: 1432-1998
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Congenital cystic adenomatoid malformation of the lung (CCAM) is an uncommon developmental abnormality presenting most often in the neonatal period. We report the clinical, radiological and pathological findings in a 9-year-old boy who presented with acute chest pain.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02015801
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  • 8
    Electronic Resource
    Electronic Resource
    Comparison of dopamine receptor antagonists on hyperlocomotion induced by cocaine, amphetamine, MK-801 and the dopamine D1 agonist C-APB in mice (1999)
    Springer
    Psychopharmacology 145 (1999), S. 237-250 
    Details
    ISSN: 1432-2072
    Keywords: Key words MK-801 ; Cocaine ; Amphetamine ; SCH23390 ; Raclopride ; Antipsychotic ; Locomotion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Rationale: Direct or indirect stimulation of dopamine receptors increases locomotor activity in mice. Determining the role played by D1 and D2 dopamine receptors in the mediation of this activity can be difficult due to the wide variety of experimental paradigms used to investigate these phenomena. Objectives: This study set out to compare the role of selective antagonism of dopamine D1 and D2 receptors on the hyperactivity induced by a range of stimulants. Methods: Mice were habituated to perspex locomotor activity boxes (30×30× 30 cm) and activity was measured via photobeam interrupts. Results: Haloperidol and clozapine both reduced the hyperactivity induced by MK-801. Haloperidol did so only at a dose that also decreased spontaneous activity (0.1 mg/kg), whereas clozapine reduced MK-801-induced hyperactivity at a dose that had no effect on spontaneous activity (1.25 mg/kg). The D1 antagonist SCH23390 (0.01 mg/kg) reduced hyperlocomotion induced by amphetamine (2.5 mg/kg), cocaine (10 mg/kg) and C-APB (1.0 mg/kg) at doses that did not consistently alter spontaneous activity, whereas the selective D2 antagonist raclopride only attenuated the hyperlocomotion induced by amphetamine, cocaine and C-APB at doses in excess of the minimum dose required to attenuate spontaneous locomotor activity significantly. The latency to peak levels of hyperlocomotion induced by MK-801 (0.3 mg/kg) was delayed by SCH23390 (0.1 mg/kg) but peak levels of activity were not reduced. Conclusions: The results of the present study suggest that selective blockade of D1 receptors suppresses amphetamine and cocaine-induced hyperactivity in mice but not MK-801-induced locomotor activity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002130051055
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  • 9
    Electronic Resource
    Electronic Resource
    RU24969-induced behavioural syndrome requires activation of both 5HT1A and 5HT1B receptors (1997)
    Springer
    Psychopharmacology 132 (1997), S. 255-260 
    Details
    ISSN: 1432-2072
    Keywords: Key words RU24969 ; 5HT1A receptors ; 5HT1B receptors ; Anpirtoline
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The behavioural profiles of the mixed 5HT1A/B agonist RU24969 and the more selective 5HT1B agonist anpirtoline were compared. Both compounds induce an increase in activity as measured in photocell activity cages. The behaviours displayed by the rats receiving each treatment differed markedly, with RU24969 inducing flat body posture and circling of the cage perimeter (1.25−10 mg/kg SC), whereas anpirtoline increased ambulation characterised by a hopping motion (1.25−5.0 mg/kg SC). The effects of RU24969 were attenuated by both the 5HT1A antagonist WAY100635 (0.03−1.25 mg/kg SC) and the 5HT1B/D antagonist GR127935 (1.0−5.0 mg/kg SC). Anpirtoline-induced behaviour was attenuated by GR127935 across the same dose range but was largely unaffected by WAY100635 even at doses above those which had blocked the effects of RU24969. Coadministration of the selective 5HT1A agonist 8-OH-DPAT (0.03−1.25  mg/kg SC) with anpirtoline (2.5 mg/kg) induced a dramatic increase in locomotor activity and a behavioural syndrome identical to that produced by RU24969. Thus it would appear that a synergistic effect of stimulation of both 5HT1A and 5HT1B receptors underlies the behavioural effects of RU24969, while anpirtoline acts mainly via stimulation of 5HT1B receptors only.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002130050343
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  • 10
    Electronic Resource
    Electronic Resource
    Alley cropping of maize with calliandra and leucaena in the subhumid highlands of Kenya: Part 2. Soil-fertility changes and maize yield (1999)
    Springer
    Agroforestry systems 46 (1999), S. 39-50 
    Details
    ISSN: 1572-9680
    Keywords: biomass transfer ; competition ; crop yield ; prunings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Although N-rich leaf biomass of multipurpose trees is known to be a good source of N to crops, integrating such trees into crop production systems is a major challenge in the development of viable agroforestry systems. An approach to integrating calliandra (Calliandra calothyrsus Meissner) and leucaena (Leucaena leucocephala (Lam.) de Wit), two promising agroforestry tree species, into maize (Zea mays L.) production system was investigated in the subhumid highlands of central Kenya during four maize-growing seasons from 1994 to 1996. The experiment consisted of maize plots to which tree prunings obtained from hedgerows grown either in situ (alley cropping) or ex situ (biomass transfer from outside) were applied. When alley-cropped with leucaena, maize produced significantly higher yields compared to maize monoculture (both non-fertilized and fertilized) treatments, but when alley-cropped with calliandra, the yield of maize was less than that of the monocropped unfertilized control. Application of ex situ grown calliandra and leucaena prunings with or without fertilizer resulted in higher maize grain yield than in the nonfertilized and fertilized treatments. Yields of calliandra alley- cropped maize were 11% to 51% lower than those of nonalley-cropped treatments receiving calliandra prunings from ex situ grown trees; the decrease was 2% to 17% with leucaena, indicating that calliandra hedges were more competitive than leucaena hedges. The alley-cropped prunings-removed treatments produced the lowest maize yields. The study showed that, in the subhumid tropical highlands of Kenya, inclusion of calliandra hedges on cropland adversely affected maize yields. On the other hand, alley cropping with leucaena was advantageous.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006288301044
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