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  • 1995-1999  (3)
  • 1985-1989  (6)
  • 1965-1969
  • 1996  (3)
  • 1988  (6)
  • 1
    Electronic Resource
    Electronic Resource
    Effects of In profile on material and device properties of AlGaAs/InGaAs/GaAs high electron mobility transistors (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 540-544 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The molecular-beam-epitaxial growth of InxGa1−xAs on GaAs or AlyGa1−yAs leads to a variation of In content with depth, due to In segregation. However, by predepositing In at the beginning of InxGa1−xAs growth, and also thermally removing the excess In at the end, we can produce a layer with the ideal "square'' In profile. We find that the performance of AlyGa1−yAs/InxGa1−xAs/GaAs high electron mobility transistors is most enhanced by the predeposition step alone. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360862
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  • 2
    Electronic Resource
    Electronic Resource
    Parametric study of AlAs/GaAs superlattice double-barrier diodes (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 53 (1988), S. 207-209 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Quantum well diodes with barriers formed by thin, short-period binary AlAs/GaAs superlattices were fabricated and found to have very high peak-to-valley current ratios. The effects of varying the AlAs and GaAs layers in the barriers are studied. The peak current density is found to decrease by orders of magnitude for monolayer increases in the AlAs layer thicknesses. Tunneling current peaks due to both resonance levels in the quantum well and resonance levels in the superlattice barriers are observed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.100132
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  • 3
    Electronic Resource
    Electronic Resource
    Characterization of AlAs/GaAs superlattice barriers using electrical barrier height analysis (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 4765-4767 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Electrical barrier height measurements on n+-GaAs–insulator–n-GaAs structures with short-period AlAs/GaAs superlattices forming the insulator show the effective conduction-band discontinuity (ΔEC) of a superlattice barrier (SLB) to be defined by the lowest superlattice energy state. Five structures with different AlAs and GaAs SLB layer thicknesses are investigated. A SLB with GaAs layers greater than 10 monolayers is found to have a ΔEC defined by Γ-valley states in the GaAs layers, while a SLB with GaAs and AlAs layers less than 10 monolayers and with thicker AlAs layers than GaAs layers is found to have a ΔEC defined by X-valley states in the AlAs layers. The SLB with GaAs and AlAs layers less than 10 monolayers and thicker GaAs layers than AlAs layers behaves as a random alloy. Negative differential resistance is observed in the current-voltage characteristic of the sample whose barrier height is defined by Γ-valley states in the GaAs layers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.341194
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  • 4
    Electronic Resource
    Electronic Resource
    Osmotic stress and abscisic acid reduce cytosolic calcium activities in roots of Arabidopsis thaliana (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 19 (1996), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Cytosolic Ca2+· ([Ca2+]i, and elongation growth were measured in the roots of Arabidopsis thaliana. Exposure of plant tissues to high NaCl and abscisic acid (ABA) concentrations results in a reduction in the rate of growth, but the mechanism by which growth is inhibited is not understood. Both NaCl and ABA treatments are known to influence [Ca2+]i, and in this study we measured the effects of salinity and ABA on [Ca2+]i in cells from the meristematic region of Arabidopsis roots. The Ca2+-sensitive dye Fura-2 and ratiometric techniques were used to measure [Ca2+]i in cells of the root meristem region. Resting [Ca2+]i was found to be between 100 and 200 μmol m−3 in roots of untreated plants. Resting [Ca2+]i changed in response to changes in the [Ca2+] surrounding growing roots. An increase of external [Ca2+] increased [Ca2+]i; conversely, a decrease of external [Ca2+] decreased [Ca2+]i. Exposure of roots to NaCl caused a rapid reduction of [Ca2+]i, a response that was proportional to the external NaCl concentration. Thus, as the NaCl concentration was increased, [Ca2+]i in root meristematic cells decreased. Root elongation was also inhibited in proportion to the external NaCl concentration, with maximal inhibition occurring at 120 mol m−3 NaCl. The [Ca2+]i of root meristem cells also changed in response to ABA, and the magnitude of the effect of ABA was dependent upon ABA concentration. Treatment with 0.2 mmol m−3 ABA caused a momentary increase in [Ca2+]i followed by a decrease after 15 min, but 10 mmol m−3 ABA caused an immediate decline in [Ca2+]i. There was a strong positive correlation between [Ca2+]i and root elongation rates. Experiments with the ABA-deficient Arabidopsis mutant aba-3 indicated that the reduction in [Ca2+]i brought about by NaCl was unlikely to be mediated via changes in endogenous ABA. Experiments with solutes such as sorbitol, KCl and NaNO3 indicated that the effects of NaCl could be mimicked by other solutes and was not specific for NaCl.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1996.tb00007.x
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  • 5
    Electronic Resource
    Electronic Resource
    Flow mechanisms in dense silica-metal oxide-water suspensions (1988)
    Springer
    Rheologica acta 27 (1988), S. 76-81 
    Details
    ISSN: 1435-1528
    Keywords: Densesuspension ; metal oxide ; silica ; settling ; plasticflow
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract The rheological properties of dense silica in water suspensions (approx. 50% solids by volume) containing additions of metal oxides were examined. Metal oxides used were ferric, zinc and stannic. To prevent settling, testing was performed in a rheometer which was modified to provide for continual stirring of the materials. Relatively small oxide additions had the effect of thickening the mixtures and making them non-Newtonian. Different rate-limiting steps for flow were identified depending on the particular mixture, testing temperature and shear strain rate. Flow could be described using empirical equations which are identical to those often used to describe plastic flow in solid crystalline materials.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01372453
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  • 6
    Electronic Resource
    Electronic Resource
    Monensin inhibits the secretion of α-amylase but not polysaccharide slime from seedling tissues ofZea mays (1988)
    Springer
    Protoplasma 142 (1988), S. 36-45 
    Details
    ISSN: 1615-6102
    Keywords: α-Amylase ; Corn (Zea mays) seedlings ; Growth ; Monensin ; Polysaccharide slime ; Secretion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The effect of monensin on polysaccharide slime secretion by root tips of corn (Zea mays) was studied. Various treatment times and ionophore concentrations were tested: none resulted in inhibition of slime secretion. Because monensin changes the pH of the medium, its effect was also monitored in strongly buffered media and at different pH's. Even in such media, monensin did not inhibit slime secretion. We also measured the effect of the drug after a pulse with [3H]fucose or a pulse followed by a chase. The amount of labeled slimed secreted was not altered by the ionophore. However, 10μM monensin affected the development of root tips and drastically reduced their growth. We showed that monensin inhibits the secretion of α-amylase by the scutellum of the same plantlet. The importance of the nature of the secretory compound in relation to monensin inhibition of its secretion is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01273224
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  • 7
    Electronic Resource
    Electronic Resource
    Effects of Ga3 and Ca2+ on barley aleurone protoplasts: a freeze-fracture study (1988)
    Springer
    Protoplasma 146 (1988), S. 157-165 
    Details
    ISSN: 1615-6102
    Keywords: Calcium ; Endomembrane system ; Enzyme secretion ; Freeze fracture ; Gibberellic acid ; Protoplasts
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Freeze-fracture electron microscopy was used to study changes in the endomembrane system of barley (Hordeum vulgare L. cv. Himalaya) aleurone protoplasts. Protoplasts were used for this study because their response to calcium and the plant hormone gibberellic acid (Ga3) can be monitored prior to rapid freezing of cells for electron microscopy. Protoplasts incubated in Ga3 plus Ca2+ secrete elevated levels of a-amylase relative to cells incubated in Ga3 or Ca2+ alone. The endoplasmic reticulum (ER) and Golgi apparatus of protoplasts incubated in Ga3 plus Ca2+ undergo changes that are well correlated with the synthesis and secretion of a-amylase. The ER, which appears as short, single sheets of membrane in Ca2+-and Ga3-treated protoplasts, exists as a series of long fenestrated stacks of membranes following incubation in Ga3 plus Ca2+. The Golgi apparatus is also more highly developed in protoplasts treated with Ga3 plus Ca2+. This organelle is larger and has more vesicles associated with its periphery in protoplasts that actively secrete a-amylase. Evidence that the Golgi apparatus participates in a-amylase secretion is also provided by experiments with the ionophore monensin, which causes pronounced swelling of Golgi cisternae and inhibits the secretion of a-amylase. We interpret these observations as showing that the ER and Golgi apparatus of barley aleurone participate in the intracellular transport and secretion of a-amylase. The plasmalemma (PF face) of barley aleurone protoplasts shows a high density of intramembranous particles (IMPs) which, in general, are evenly distributed. Occasionally, ordered arrays of IMPs are observed, possibly resulting fro m osmotic stress. after 48 hours the plasmalemma of some Ga3-treated protoplasts show particle-free areas considered to be indications of senescence.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01405925
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  • 8
    Electronic Resource
    Electronic Resource
    The effect of salbutamol on performance in endurance cyclists (1996)
    Springer
    European journal of applied physiology 73 (1996), S. 364-368 
    Details
    ISSN: 1439-6327
    Keywords: Salbutamol ; Ergogenic aid ; Oxygen uptake kinetics ; Cycling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effect of salbutamol (S) on cycling performance was examined in 15 highly trained non-asthmatic male cyclists. A double-blind, randomized cross-over design was used with S or placebo (P) administered using a metered-dose inhaler and a spacer device 20 min before each testing session. The S dose was 400 μg (four puffs), which is twice the normal therapeutic level. Subjects were habituated to all the laboratory procedures in the week prior to actual data collection. The subjects performed four tests under S and P conditions on separate days over 2 weeks. These included measurement of maximal O2 uptake $$(\dot VO_{2max} )$$ (cycle ergometry) with assessment of pulmonary function before and after, a submaximal (90% of ventilatory threshold) square-wave work transition from a base of unloaded cycling, a 60-s modified Wingate test, and a simulated 20 km time trial. No significant differences were observed in any of the dependent variables related to aerobic endurance or cycling performance between the S and P conditions. These results support other findings that an acute dose (400 μg) of S has no performance-enhancing properties.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02425500
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  • 9
    Electronic Resource
    Electronic Resource
    Effect of solids concentration in dense suspensions of silica-iron(III) oxide and water (1988)
    Springer
    Rheologica acta 27 (1988), S. 197-201 
    Details
    ISSN: 1435-1528
    Keywords: Densesuspension ; power-lawflow ; entropy ; iron oxide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract The rheological properties of dense suspensions, of silica, iron (III) oxide and water, were studied over a range of solids concentrations using a viscometer, which was modified so as to prevent settling of the solid components. Over the conditions studied, the material behaved according to power—law flow relationships. As the concentrations of silica and iron(III) oxide were increased, an entropy term in the flow equation was identified which had a silica dependent and an iron (III) oxide dependent component. This was attributed to a tendency to order into some form of structural regularity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01331905
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