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  • 1
    Electronic Resource
    Electronic Resource
    Expression of calcium channel subunits in the normal and diseased human myocardium (1996)
    Springer
    Journal of molecular medicine 74 (1996), S. 99-104 
    Details
    ISSN: 1432-1440
    Keywords: L-type calcium channel ; β Subunit isoforms ; Human heart ; Cardiac hypertrophy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We investigated the expression of α1 and β subunits of the L-type Ca2+ channel on the protein level in cardiac preparations from normal human heart ventricles and from the hypertrophied septum of patients with hypertrophic obstructive cardiomyopathy (HOCM). 1,4-Dihydropyridine (DHP) binding and immunorecognition by polyclonal antibodies directed against the C-terminal amino acid sequences of the β2 and β3 subunits were used for detection and quantification of α1, β2, and β3 subunits. Bmax of high-affinity DHP binding was 35±2 fmol/mg protein in HOCM and 20±2 fmol/mg protein in normal human hearts (P〈0.05). In rabbit hearts the anti-β2 subunit antibody immunoprecipitated 80% of the total amount of DHP-labeled Ca2+ channels present in the assay. Under identical experimental conditions 25% of labeled Ca2+ channels were recovered in the immunoprecipitates of both normal and HOCM ventricles. A similar partial immunoprecipitation was observed in pig hearts. Immunoblot analysis demonstrated that the β2 subunit was associated with the DHP receptor/Ca2+ channel in cardiac muscle of rabbit, pig, and human heart. In neither of these purified cardiac Ca2+ channels was the β3 subunit isoform detected. Our results suggest that both α1 and β2 subunit expression is upregulated in HOCM in a coordinate manner.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00196785
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  • 2
    Electronic Resource
    Electronic Resource
    A Raman spectroscopic study of the Si, Be, and C incorporation in InxGa1−xAs relaxed layers (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 4690-4695 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The incorporation of high concentrations ((approximately-greater-than)1019 cm−3) of Si, Be, and C in InxGa1−xAs relaxed layers has been studied as a function of In content (x≤0.16) by Raman spectroscopy of local vibrational modes (LVM). The frequencies of the Raman peaks resulting from the convolution of several split modes shift to lower values as the In content is increased, the carbon acceptor (CAs) local mode frequency showing the strongest dependency on x. Features attributed exclusively to the influence of In on second-neighbor sites are identified only in the Si-doped samples. The transverse and longitudinal modes expected from the splitting of a LVM of CAs with one In first neighbor are not observed in layers with x up to 0.085. A new calibration for the BeGa, CAs, and Si-related LVM leads to the conclusion that In increases the total electrical activation of Si and favors its incorporation on group-III sublattice sites. In contrast, no influence of In on the Be or C doping activation has been detected. The analysis of the CAs LVM spectra supports the view that in InxGa1−xAs CAs is preferably surrounded by Ga instead of In atoms for x≤0.085. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359816
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  • 3
    Electronic Resource
    Electronic Resource
    Solid-solubility limits of Be in molecular beam epitaxy grown AlxGa1−xAs layers and short-period superlattices (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 4312-4315 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The redistribution of Be in highly doped AlxGa1−xAs layers and AlxGa1−xAs/AlAs(GaAs) short period superlattices (SPSL) during molecular beam epitaxy was investigated by secondary ion mass spectrometry (SIMS) depth profiling. Be outdiffuses significantly from these layers and, additionally, segregates in growth direction. Conversely, Be is depleted and incorporated only up to a solid-solubility limit depending on the Al content. SPSLs with shorter period are disordered and show the solid-solubility limits of homogeneous AlxGa1−xAs layers with the same average composition. Be solid-solubility limits in AlxGa1−xAs layers covering the whole range from GaAs to AlAs are derived from the SIMS depth profiles. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.371362
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  • 4
    Electronic Resource
    Electronic Resource
    Current dependence of grain boundary magnetoresistance in La0.67Ca0.33MnO3 films (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 2173-2177 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We prepared epitaxial ferromagnetic manganite films on 45° bicrystal substrates by pulsed laser ablation. Their low- and high-field magnetoresistance (MR) was measured as a function of magnetic field, temperature and current. At low temperatures hysteretic changes in resistivity up to 70% due to switching of magnetic domains at the coercitive field are observed. The strongly nonohmic behavior of the current–voltage leads to a complete suppression of the MR effect at high bias currents with the identical current dependence at low and high magnetic fields. We discuss the data in view of tunneling and mesoscale magnetic transport models and propose an explicit dependence of the spin polarization on the applied current in the grain boundary region. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.371026
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  • 5
    Electronic Resource
    Electronic Resource
    Effect of strain and associated piezoelectric fields in InGaN/GaN quantum wells probed by resonant Raman scattering (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 74 (1999), S. 3863-3865 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The influence of pseudomorphic strain and resulting piezoelectric fields on In0.13Ga0.87N/GaN quantum wells has been studied by resonant Raman scattering. The A1(LO) phonon of In0.13Ga0.87N pseudomorphically strained to GaN is found to be downshifted in frequency by only 3 cm−1 with respect to GaN, which gives evidence for a near cancellation between the much larger frequency downshift of 10 cm−1 reported for unstrained In0.13Ga0.87N and a high-frequency shift of the A1(LO) phonon induced by the in-plane compressive strain. For excitation in resonance with the fundamental interband transition of the InGaN well, the intensity of first- and second-order scattering by the InGaN A1(LO) phonon was found to decrease with decreasing excitation power density, and thus increasing strength of the piezoelectric field. This finding is explained by a quenching of the excitonic enhancement in the resonance profile by the piezoelectric field. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.124205
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  • 6
    Electronic Resource
    Electronic Resource
    Carrier profile for In0.35Ga0.65As/GaAs multiquantum well lasers from capacitance–voltage measurements (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 1138-1140 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The carrier profile for MBE grown In0.35Ga0.65As/GaAs multiquantum well laser structures with nominally undoped and beryllium-doped active regions was determined by using the capacitance–voltage (C–V) technique at room temperature. A simple theoretical model was used to extract the impurity concentration and the quantum-well carrier density from the experimental profiles. We obtained a high carrier concentration in nominally undoped devices caused by a strong growth temperature dependent Be diffusion from the p-cladding layer, and no difference between doped samples with different nominal dopant location. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.115738
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  • 7
    Electronic Resource
    Electronic Resource
    Determination of the bonding of carbon acceptors in InxGa1−xAs for x〈0.1 (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 66 (1995), S. 2676-2678 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The local environment of CAs acceptors in InxGa1−xAs has been determined from the localized vibrational modes (LVMs) of both isolated CAs impurities and H–CAs pairs using infrared (IR) absorption and Raman scattering techniques. In as-grown layers, a single LVM due to CAs was observed which broadened and shifted to lower energies with increasing x. The introduction of hydrogen led to the formation of H–CAs pairs and a single antisymmetric A1− mode (stretch) and a single symmetric A+1 mode (XH) were observed for all samples. All the LVMs were identified with carbon in CAsGa4 cluster configurations implying that less than 5% of the detectable carbon atoms are present in clusters incorporating one or more CAs–In bonds. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.113122
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  • 8
    Electronic Resource
    Electronic Resource
    Nature of the 2.8 eV photoluminescence band in Mg doped GaN (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 72 (1998), S. 1326-1328 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The blue Mg induced 2.8 eV photoluminescence (PL) band in metalorganic chemical vapor deposition grown GaN has been studied in a large number of samples with varying Mg content. It emerges near a Mg concentration of 1×1019 cm−3 and at higher concentrations dominates the room temperature PL spectrum. The excitation power dependence of the 2.8 eV band provides convincing evidence for its donor–acceptor (D–A) pair recombination character. It is suggested that the acceptor A is isolated MgGa while the spatially separated, deep donor (430 meV) D is attributed to a nearest-neighbor associate of a MgGa acceptor with a nitrogen vacancy, formed by self-compensation. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.120983
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  • 9
    Electronic Resource
    Electronic Resource
    Realization and modeling of a pseudomorphic (GaAs1−xSbx–InyGa1−yAs)/GaAs bilayer-quantum well (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 2639-2641 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have realized a (GaAs1−xSbx-InyGa 1−yAs)/GaAs bilayer-quantum well (BQW), which consists of two adjacent pseudomorphic layers of GaAs1−xSbx and InyGa1−yAs sandwiched between GaAs barriers. Photoluminescence was observed at longer wavelengths than those found for corresponding InyGa1−yAs/GaAs and GaAs1−xSbx/GaAs single quantum wells (SQW), which indicates a type-II band alignment in the BQW. The longest 300 K emission wavelength achieved so far was 1.332 μm. For an accurate determination of the band offset between GaAs1−xSbx and GaAs, required for a theoretical modeling of the interband transition energies of these BQWs, a large set of GaAs1−xSbx /GaAs SQWs was prepared from which a type-II band alignment was deduced, with the valence band discontinuity ratio Qv found to depend on the Sb concentration x (Qv=1.76+1.34 x). With this parameter it was possible to calculate the expected interband transition energies in a BQW structure without any adjustable parameters. The calculations are in agreement with experimental data within a range of ±4%. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.114321
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  • 10
    Electronic Resource
    Electronic Resource
    Effects of oligonucleotide adsorption on the physicochemical characteristics of a nanoparticle-based model delivery system for antisense drugs (1999)
    Springer
    Colloid & polymer science 277 (1999), S. 145-152 
    Details
    ISSN: 1435-1536
    Keywords: Key words Nanoparticles ; Drug carrier ; Colloidal stability ; Oligonucleotides ; Zeta potential
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Cationic polystyrene nanoparticles, as a model drug carrier system for nucleic acids, are capable of binding negatively charged oligonucleotides by multiple electrostatic interactions. The effect of the adsorption of phosphorothioate oligonucleotides on the physicochemical properties of the carrier system was investigated for uncoated and sterically stabilized latex particles. Turbidity measurements and photon-correlation spectroscopy indicate that the colloidal stability of the nanoparticle-oligonucleotide conjugates is influenced by the number of oligonucleotides adsorbed on the carrier. Especially in the case of the uncoated material, a destabilizing effect has been observed up to oligonucleotide concentrations of 2.7 μmol/g polymer. Strikingly, at higher concentrations the latexes exhibit colloidal stability similar to the oligonucleotide-free samples. These results were correlated to zeta-potential measurements demonstrating a reversal from positive to negative values of the zeta potential with increasing oligonucleotide concentration. The points of zero charge of the particles are in the region of maximum coagulation. These findings were compared to adsorption studies and calculations based on the random sequential adsorption model. It appears that at first the colloidal stability of the carrier systems is diminished with increasing oligonucleotide adsorption, while higher surface coverages lead to a significant reduction in coagulation. At the saturation level the surface coverage can be considered as a monolayer of “side-on” adsorbed molecules and the conjugates exhibit colloidal stability similar to the bare particles without adsorbed molecules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003960050379
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