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  • 1
    Electronic Resource
    Electronic Resource
    Device model investigation of bilayer organic light emitting diodes (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 1974-1982 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Organic materials that have desirable luminescence properties, such as a favorable emission spectrum and high luminescence efficiency, are not necessarily suitable for single layer organic light-emitting diodes (LEDs) because the material may have unequal carrier mobilities or contact limited injection properties. As a result, single layer LEDs made from such organic materials are inefficient. In this article, we present device model calculations of single layer and bilayer organic LED characteristics that demonstrate the improvements in device performance that can occur in bilayer devices. We first consider an organic material where the mobilities of the electrons and holes are significantly different. The role of the bilayer structure in this case is to move the recombination away from the electrode that injects the low mobility carrier. We then consider an organic material with equal electron and hole mobilities but where it is not possible to make a good contact for one carrier type, say electrons. The role of a bilayer structure in this case is to prevent the holes from traversing the device without recombining. In both cases, single layer device limitations can be overcome by employing a two organic layer structure. The results are discussed using the calculated spatial variation of the carrier densities, electric field, and recombination rate density in the structures. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.372123
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  • 2
    Electronic Resource
    Electronic Resource
    Symptomatic and Disease Modifying Treatments of Alzheimer's Disease (2000)
    Oxford, UK : Blackwell Publishing Ltd
    CNS drug reviews 6 (2000), S. 0 
    Details
    ISSN: 1527-3458
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1527-3458.2000.tb00168.x
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  • 3
    Electronic Resource
    Electronic Resource
    Mechanisms of 5-Aminolevulinic Acid Uptake at the Choroid Plexus (2000)
    Oxford UK : Blackwell Science Ltd.
    Journal of neurochemistry 75 (2000), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract : 5-Aminolevulinic acid (5-ALA) is a precursor of porphyrins and heme that has been implicated in the neuropsychiatric symptoms associated with porphyrias. It is also being used clinically to delineate malignant gliomas. The blood-CSF barrier may be an important interface for 5-ALA transport between blood and brain as in vivo studies have indicated 5-ALA is taken up by the choroid plexuses whereas the normal blood-brain barrier appears to be relatively impermeable. This study examines the mechanisms of 5-[3H]ALA uptake into isolated rat lateral ventricle choroid plexuses. Results suggest that there are two uptake mechanisms. The first was a Na+-independent uptake system that was pH dependent (being stimulated at low pH). Uptake was inhibited by the dipeptide Gly-Gly and by cefadroxil, an α-amino-containing cephalosporin. These properties are the same as the proton-dependent peptide transporters PEPT1 and PEPT2, which have recently been shown to transport 5-ALA in frog oocyte expression experiments. Choroid plexus uptake was not inhibited by captopril, a PEPT1 inhibitor, suggesting PEPT2-mediated uptake. The presence of PEPT2 and absence of PEPT1 in the choroid plexus were confirmed by western blotting. The second potential mechanism was both Na+ and HCO3- dependent and appears to be an organic anion transporter, although it is possible that removal of Na+ and HCO3- may indirectly affect PEPT2 by affecting intracellular pH. The presence of PEPT2 and a putative Na+/HCO3--dependent organic anion transporter is important not only for an understanding of 5-ALA movement between blood and brain but also because these transporters may affect the distribution of a number of drugs between blood and CSF.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1471-4159.2000.0750321.x
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  • 4
    Electronic Resource
    Electronic Resource
    Optical properties of single carrier polymer diodes under high electrical injection (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 78 (2001), S. 270-272 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present measurements of the modulation of the near absorption edge optical properties of single carrier diodes made from a soluble poly(p-phenylene vinylene) derivative. Pulsed electrical excitation was used to acquire the optical characteristics for average injected charge densities up to 1018 cm−3. For injected carrier densities below 5×1017 cm−3, the modulation of the optical properties are dominated by electroabsorption effects; at higher densities, the effects of the injected charge predominate. We find that there is no significant absorption by the injected charge below the optical absorption threshold and that there is substantial bleaching of the lowest energy optical transitions at high carrier density. These results imply that charge carrier absorption in this polymer does not limit the performance of organic light-emitting diodes and diode lasers. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1340859
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  • 5
    Electronic Resource
    Electronic Resource
    Laser-assisted scanning tunnelling microscope detection of a molecular adsorbate (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 76 (2000), S. 3825-3827 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Optical excitation has been combined with the scanning tunneling microscope and a laser-induced change in the tunneling gap width of about 0.25 Å, shows a resonance effect with the electronic absorption of the sample, a monolayer of the J-aggregating dye 1,1′-diethyl-2,2′-cyanine bromide on a silver substrate. The strength of the effect is reduced by spacing the J aggregate away from the silver substrate using a carboxylic acid functionalized alkylthiol self-assembled monolayer. We propose that the origin of the resonant response is the nonradiative decay of the molecular excited state into the underlying metal substrate that causes local heating and thermal expansion. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.126794
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  • 6
    Electronic Resource
    Electronic Resource
    Microwave transmission through a two-dimensional, isotropic, left-handed metamaterial (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 78 (2001), S. 489-491 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present experimental data, numerical simulations, and analytical transfer-matrix calculations for a two-dimensionally isotropic, left-handed metamaterial (LHM) at X-band microwave frequencies. A LHM is one that has a frequency band with simultaneously negative cursive-epsiloneff(ω) and μeff(ω), thereby having real values of index of refraction and wave vectors, and exhibiting extended wave propagation over that band. Our physical demonstration of a two-dimensional isotropic LHM will now permit experiments to verify some of the explicit predictions of reversed electromagnetic-wave properties including negative index of refraction as analyzed by Veselago [Usp. Fiz. Nauk 92, 517 (1964), Sov. Phys. Usp. 10, 509 (1968)]. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1343489
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  • 7
    Electronic Resource
    Electronic Resource
    Direct calculation of permeability and permittivity for a left-handed metamaterial (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 77 (2000), S. 2246-2248 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Recently, an electromagnetic metamaterial was fabricated and demonstrated to exhibit a "left-handed" (LH) propagation band at microwave frequencies. A LH metamaterial is one characterized by material constants—the permeability and permittivity—which are simultaneously negative, a situation never observed in naturally occurring materials or composites. While the presence of the propagation band was shown to be an inherent demonstration of left handedness, actual numerical values for the material constants were not obtained. In the present work, using appropriate averages to define the macroscopic fields, we extract quantitative values for the effective permeability and permittivity from finite-difference simulations using three different approaches. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1314884
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  • 8
    Electronic Resource
    Electronic Resource
    TURBIDITY SUSPENI)ED SEDIMENT, AND WATER CLARITY: A REVIEW (2001)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the American Water Resources Association 37 (2001), S. 0 
    Details
    ISSN: 1752-1688
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Notes: : Suspended sediment causes a range of environmental damage, including benthic smothering, irritation of fish gills, and transport of sorbed contaminants. Much of the impact, while sediment remains suspended, is related to its light attenuation, which reduces visual range in water and light availability for photosynthesis. Thus measurement of the optical attributes of suspended matter in many instances is more relevant than measurement of its mass concentration. Nephelometric turbidity, an index of light scattering by suspended particles, has been widely used as a simple, cheap, instrumental surrogate for suspended sediment, that also relates more directly than mass concentration to optical effects of suspended matter. However, turbidity is only a relative measure of scattering (versus arbitrary standards) that has no intrinsic environmental relevance until calibrated to a ‘proper’ scientific quantity. Visual clarity (measured as Secchi or black disc visibility) is a preferred optical quantity with immediate environmental relevance to aesthetics, contact recreation, and fish habitat. Contrary to common perception, visual clarity measurement is not particularly subjective and is more precise than turbidity measurement. Black disc visibility is inter-convertible with beam attenuation, a fundamental optical quantity that can be monitored continuously by beam transmissometry. Visual clarity or beam attenuation should supplant nephelometric turbidity in many water quality applications, including environmental standards.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1752-1688.2001.tb03624.x
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  • 9
    Electronic Resource
    Electronic Resource
    Prospective randomised double-blind comparative study of rocuronium and pancuronium in adult patients scheduled for elective ‘fast-track’ cardiac surgery involving hypothermic cardiopulmonary bypass (2003)
    Oxford, UK : Blackwell Science Ltd
    Anaesthesia 58 (2003), S. 0 
    Details
    ISSN: 1365-2044
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Summary The majority of cardiac anaesthetists in the UK use pancuronium for fast-track cardiac surgery. We compared the duration of action of pancuronium and rocuronium in patients undergoing fast- track hypothermic cardiopulmonary bypass and cardiac surgery. We determined whether patients would have had residual neuromuscular blockade at extubation. Twenty patients were randomly allocated to receive either pancuronium 0.1 mg.kg−1 or rocuronium 1 mg.kg−1. Neuromuscular function was assessed by acceleromyography; spontaneous recovery was evaluated by the train-of-four ratio measured at the adductor pollicis longus muscle. Median times to recover train-of-four ratio of 0.9 were 3 h 38 min for rocuronium and 7 h 52 min for pancuronium. The median difference in recovery times was 4 h 15 min (95% CI 2 h 30 min to 6 h 20 min; p = 0.0003 by Mann–Whitney test). None of the patients in the rocuronium group and seven of 10 patients in the pancuronium group had their extubations delayed because of residual neuromuscular blockade. Unless fast-track patients have neuromuscular function assessed before extubation, pancuronium should not be used.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2044.2003.30362.x
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  • 10
    Electronic Resource
    Electronic Resource
    Shape effects in plasmon resonance of individual colloidal silver nanoparticles (2002)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 116 (2002), S. 6755-6759 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We present a systematic study of the effect of size and shape on the spectral response of individual silver nanoparticles. An experimental method has been developed that begins with the detection and characterization of isolated nanoparticles in the optical far field. The plasmon resonance optical spectrum of many individual nanoparticles are then correlated to their size and shape using high-resolution transmission electron microscopy. We find that specific geometrical shapes give distinct spectral responses. In addition, inducing subtle changes in the particles' morphology by heating causes a shift in the individual particle spectrum and provides a simple means of tuning the spectral response to a desired optical wavelength. Improved colloidal preparation methods could potentially lead to homogeneous populations of identical particle shapes and colors. These multicolor colloids could be used as biological labels, surface enhanced Raman scattering substrates, or near field optical microscopy sources covering the full range of wavelengths in the visible spectrum. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1462610
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