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  • 1
    Electronic Resource
    Electronic Resource
    The Response of the Tyrosine Hydroxylase Gene to Cyclic AMP Is Mediated by Two Cyclic AMP-Response Elements (1995)
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 65 (1995), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Tyrosine hydroxylase (TH) gene transcription rate is stimulated by cyclic AMP in cultured rat pheochromocytoma cells. This effect is at least partially due to the interaction of transcription factors with the canonical cyclic AMP-response element (CRE) at position −45 to −38 within the TH gene promoter. In this study we test whether a region of the TH gene promoter, which is adjacent to and upstream of the canonical TH CRE, also participates in the response of the promoter to cyclic AMP. Using electrophoretic mobility shift assays, we demonstrate that nuclear proteins from rat pheochromocytoma cell lines bind to the region of the TH gene from −102 to −73. A comparison of promoter sequences indicates that sequences within this region of the TH gene are highly homologous to proenkephalin promoter sequences (between −110 and −80) designated ENKCRE-1 and ENKCRE-2. We designated the TH gene sequence homologous to ENKCRE-1 as TH E1 and the sequence homologous to ENKCRE-2 as TH E2. Competition displacement binding assays suggest that protein binding to the −102/−73 region of the TH gene is critically dependent on the TH E1 sequence. Transient transfection assays using minimal promoter constructs demonstrate that this region acts as a cyclic AMP-responsive element. Mutagenesis of the TH E1 sequence within the normal context of the TH gene proximal promoter leads to a 50% decrease in the cyclic AMP inducibility of the promoter. These results support the hypothesis that the full response of the TH gene to cyclic AMP requires both the canonical TH CRE and this newly discovered element, which we term TH CRE2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1471-4159.1995.65051934.x
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  • 2
    Electronic Resource
    Electronic Resource
    Photothermal deflection and photoluminescence studies of CdS and CdSe quantum dots (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 3041-3044 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report on the observation of the quantum confinement effect by using photothermal deflection spectroscopy (PDS) experiment and the time dependence of optically induced degradation in CdS and CdSe semiconductor-doped glasses. The observed absorption peaks in the PDS experiment, together with a simple model, were used to evaluate the average radius of semiconductor microcrystals. It is found that the estimated average radii of quantum dots are consistent with that obtained from other methods. This result demonstrates that the PDS technique provides an alternative tool for the study of the optical properties of semiconductor microscrystals. The time dependence of the luminescence degradation of the impurity band, which is attributed to the process of Auger ionization, follows a stretched-exponential function. The inconsistency with the previously proposed exponential relaxation may be due to the size distribution of CdS and CdSe microcrystals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357483
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  • 3
    Electronic Resource
    Electronic Resource
    Morphologies and photoluminescence of porous silicon under different etching and oxidation conditions (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 7728-7736 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: It is found from scanning electron microscopy that the porous silicon samples fabricated under different conditions exhibit different morphologies. Some of them show islands or cracks, but the rest appear to be smooth. It is proposed that the formation of the islands and the cracks depends on the porosity of the porous silicon samples and result from the shrinkage of the porous structure. The photoluminescence spectra of the porous silicon samples also depend on the etching conditions. The peak position of the photoluminescence shifts to higher energy with increasing the porosity of the samples or by rinsing the samples in deionized water for a long time. However, in certain situations the photoluminescence peak shifts to lower energy after the samples are placed in air for a couple of days. It is proposed that not only the quantum size effect but also the transition between oxide levels contribute to the photoluminescence of the porous silicon.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356604
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  • 4
    Electronic Resource
    Electronic Resource
    Observation of the singlet–triplet pair of the 4p Rydberg state and assignment of the Rydberg series of SO2 (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 112 (2000), S. 2210-2217 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The triplet g˜ Rydberg state of SO2 with an origin at 78 245.8 cm−1, 526 cm−1 below the previously detected singlet G˜ state origin, has been observed in a two-color resonantly enhanced multiphoton ionization experiment. The bending vibrational levels (v=0–5 with intervals of 400±10 cm−1) has been identified and reported. Based on the symmetry, bending frequencies, quantum defects, and term values, this G˜ state singlet–triplet pair was assigned to the sulfur 4p state belonging to the series converging to the SO2+ X˜ 2A1 state. The same procedure also allows the reassignment of the Rydberg state previously observed in the 111.5–115 nm region to the sulfur 4p orbital (converging to the SO2+ A˜ 2A2 state) and the one in the 106.3–110.4 nm region to the 5p orbital (converging to the SO2+ X˜ 2A1 state). The spectral patterns also indicate that the G˜ states have a detectable increase in the dissociation rate above the v2=2 level. The triplet state near the 193 nm region is dissociative with a homogeneous width of ∼13 cm−1. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.480787
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  • 5
    Electronic Resource
    Electronic Resource
    The fluorescence excitation spectra of the A 1Au(S1)–X 1Ag(S0) transition of biacetyl: Determination of the band origin (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 111 (1999), S. 6650-6651 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Laser-induced fluorescence spectra of the A 1Au(S1)–X 1Ag(S0) transition of biacetyl are observed under supersonic jet condition. Three weaker bands have been observed at 154, 67, and 58 cm−1 to the red of the previously presumed band origin 000 (at 22 336 cm−1). The observed tunneling splitting 1.05 cm−1 for the G01 band and 1.68 cm−1 for the A01 band are compared to the theoretical result. Based on the tunneling splitting, the true band origin 000 is determined for the first time as the furthest weaker band at 22 182 cm−1. The three weaker bands have been assigned as 000, G01, and A01 transitions, respectively. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.480013
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  • 6
    Electronic Resource
    Electronic Resource
    Preparation of the partially substituted (phenoxy)chlorocyclotriphosphazenes by phase-transfer catalysis (1991)
    s.l. : American Chemical Society
    Industrial & engineering chemistry research 30 (1991), S. 1314-1319 
    Details
    ISSN: 1520-5045
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ie00054a036
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  • 7
    Electronic Resource
    Electronic Resource
    An explanation of optically induced excess conductivity in compensated a-Si:H films (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 62 (1987), S. 2578-2579 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In order to explore the creation process of optically induced excess conductivity in compensated a-Si:H films, we investigated the effect of monochromatic light exposure with different photon energies: 2.54, 1.96, 1.17, and 0.95 eV. The experimental results show that the threshold energy is below 0.95 eV. We suggest that the most likely explanation is the introduction of localized states originating from boron-phosphorus complexes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.339431
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  • 8
    Electronic Resource
    Electronic Resource
    Material and electrical properties of highly mismatched InxGa1−xAs on GaAs by molecular-beam epitaxy (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 6912-6918 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The material properties of 2-μm-thick InxGa1−xAs epilayers grown on GaAs with 0.28≤x≤1 were investigated. It was found that for x≥0.5, the material quality of the larger lattice-mismatched heterojunction recovers, as evidenced by cross-sectional transmission electron microscopy (XTEM) and double-crystal x-ray diffraction (DXRD). Magnetophotoconductivity measurements were performed on InxGa1−xAs epilayers with 0.75≤x≤1. The dependence of both the cyclotron resonance linewidth and the carrier relaxation time on the material quality is consistent with the XTEM and DXRD results. The transport properties of InxGa1−xAs epilayers with 0.75≤x≤1 were studied using temperature-dependent van der Pauw measurements. It was found that the electron mobility in the low-temperature range is determined by a combination of ionized impurity and dislocation scatterings. The contribution of dislocation scattering to ternary InGaAs epilayers is larger than that to InAs, although InAs has a larger lattice mismatch with respect to GaAs. These four different measurement techniques confirm that the growth mode rather than lattice mismatch determines the density of dislocation for the heteroepitaxy of highly mismatched InxGa1−xAs on GaAs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355065
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  • 9
    Electronic Resource
    Electronic Resource
    Photoconduction of synthetic pyrite FeS2 single crystals (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 2786-2789 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The photoconduction of synthetic pyrite FeS2 single crystals with low impurity concentration prepared by chemical vapor transport method is reported over a temperature range from 15 K to 300 K. The energy gap is determined from the photoconductive spectral response by the Moss rule. At room temperature the indirect energy gap is found to be 0.83±0.02 eV. According to the experimental evidence for a sharp antibonding p-like state above the Fermi level of FeS2 reported by Folkerts et al. [J. Phys. C 20, 4135 (1987)], the indirect gap is assigned as the transition between Fe 3d t2g and S 3p σ* states. The temperature variation of the indirect band gap shows a linear dependence between 100 K and 300 K with a negative temperature coefficience equal to 1.0±0.1 meV/K. A distinct feature at higher energy side of the spectrum is observed and attributed to the direct band-gap transition. At temperature lower than 60 K, a very sharp peak around 0.9 eV emerged below the absorption edge. This feature might be associated with the excess carriers induced by the photothermal ionization between the impurity levels and conduction band.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354627
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  • 10
    Electronic Resource
    Electronic Resource
    Investigation of collisional quenching of CCl2 (A˜ 1B1 and a˜ 3B1) by alkanes (2001)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 114 (2001), S. 10798-10804 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: CCl2 free radicals were produced by a pulsed dc discharge of CCl4 (in Ar). Ground electronic state CCl2(X˜) radical was electronically excited to A˜ 1B1(0,4,0) vibronic state by Nd:YAG laser pumped dye laser at 541.52 nm. The laser induced fluorescence signal is observed to be a monoexponential decay curve corresponding to the decay of the A˜ state under supersonic jet conditions and the lifetime of CCl2(A˜→X˜) transition was measured being 0.83±0.03 μs. Experimental quenching data of excited CCl2(A˜ 1B1 and a˜ 3B1) by alkanes were obtained by observing the time-resolved total fluorescence signal of the excited CCl2 radical in a cell, which showed a superposition of two exponential components under the presence of a quencher. The quenching rate constants of A˜(1B1) and a˜(3B1) states of CCl2, KA, and Ka, were derived by analyzing the experimental data according to a proposed three-level model to deal with the CCl2(X˜ 1A1,A˜ 1B1,a˜ 3B1) system. KA and Ka increase steadily by increasing the number of C–H bonds contained in the alkane molecules. The formation cross sections of the complexes of electronically excited CCl2 radicals and alkane molecules were calculated by means of a collision complex model. It is shown that the dependence of the formation cross section of the complex on the number of C–H bonds contained in the alkane molecule is in agreement with that of the measured quenching cross section. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1377029
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