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  • 1
    Electronic Resource
    Electronic Resource
    Interference dips in molecular absorption spectra calculated for coupled electronic state potential surfaces (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 96 (1992), S. 2681-2690 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Interference effects in electronic absorption spectra caused by coupling between excited states are calculated and interpreted by using numerical integration of the time-dependent Schrödinger equation and the time-dependent theory of electronic spectroscopy. The interference between nearby spin-forbidden doublet and spin-allowed quartet states of chromium (III) and vanadium (II) metal complexes causes sharp decreases of intensity or dips in the envelopes of absorption bands. The states are coupled by spin–orbit coupling. The origin of the dips is explained in terms of interference between wave packets moving on potential energy surfaces representing the states. The importance of curve crossing and amplitude transfer between the states is analyzed quantitatively. The theory is applied to the absorption spectrum of a chromium (III) complex.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.462016
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Lamb dip and infrared–radio frequency double resonance spectroscopy of 188OsO4 (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 2509-2512 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The frequency of seven rovibrational transitions in the ν3 band, Q branch of 188OsO4 have been measured with high accuracy. The spectrometer used consists of two CO2 lasers [∼3 W on the 10R(0)], the first of which is stabilized on the 4.3 μm fluorescence Lamb dip of the CO2 and the second on the saturated absorption dip of the rovibrational transitions of 188OsO4. The OsO4 transition frequencies are obtained combining the known frequency of the first laser with the measured frequency of the beat note between the two laser beams. For the assignment of the transitions the recent Fourier transform analysis by Bobin et al. [J. Mol. Spectrosc. 122, 229 (1987)] was used. The access to the 10R(0) laser line has made it possible to investigate, for the first time, the Q branch of the ν3 band of OsO4 in a sub-Doppler regime. Furthermore, the tetrahedral fine structure in the ground and in the ν3 state has been analyzed using the infrared–radio frequency double resonance technique. The tetrahedral splitting constants, Dt for the ground state and Z3t for the ν3 state, have been calculated with higher accuracy than in previous works.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.459875
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  • 3
    Electronic Resource
    Electronic Resource
    Laser-assisted organometallic chemical vapor deposition of films of rhodium and iridium (1992)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 60 (1992), S. 1402-1403 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: High purity (less than 1% carbon) thin films of rhodium and iridium metal have been obtained by laser-assisted organometallic chemical vapor deposition. Gaseous (η5-C5H5)M(C2H4)2 (M=Rh,Ir) was the organometallic precursor. Depositions were carried out in an atmosphere of He and H2 at room temperature and atmospheric pressure. Wavelength dependence studies of the rhodium precursor have shown that only irradiation into the compound's charge transfer band causes deposition. Deposits can also be obtained thermally. The films were analyzed by x-ray diffraction and x-ray photoelectron spectroscopy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.107304
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  • 4
    Electronic Resource
    Electronic Resource
    Clustered water adsorption on the NaCl(100) surface (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 98 (1993), S. 10049-10060 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The adsorption dynamics of water on NaCl(100) is studied by molecular dynamics calculations as a function of coverage. We find that, starting from a critical coverage of about 1/2 monolayer, a coupling of the water dipoles sets in and the interaction between the water molecules wins over the interaction between adsorbate and substrate leading via percolation to formation of infinite cluster networks. This effect is confirmed qualitatively by surface sensitive optical second harmonic measurements with well-controlled water exposure. At a coverage of one bilayer, a two-dimensional "ice'' structure is found to be stable. Simulated low-energy electron diffraction (LEED) patterns for this configuration are in excellent agreement with recent observation of a c(4×2) overstructure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.464438
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  • 5
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    Excited state mixed valence in a dual-bridged three-chromophore system (2012)
    Wiley
    Details
    Publication Date: 2012-04-15
    Description: The optical and resonance Raman spectra of the 2,2′: 6′,2″:6″,6-trioxytriphenyl-amine cation are measured and interpreted. This molecule contains two simultaneous types of coupling between three chromophores and two types of bridging atoms. The first and conventional coupling involves a single nitrogen bridge that couples all three aryl groups. The second is provided by the three oxygen atoms, each of which bridges two adjacent aryl groups. There are two bands in the visible region of the optical absorption spectrum; their assignment and the interpretation of the contributing orbitals and electronic states are described in terms of the neighboring orbital model that explains the effects of the two types of coupling. The bonding changes that take place in the excited electronic states are probed by resonance Raman spectroscopy intensities and analyzed using the time-dependent theory of resonance Raman spectroscopy. The optical absorption spectrum was fit using the measured vibrational frequencies and excited state distortions. The distortions correlate well with the bonding changes predicted by the neighboring orbital model. The resonance Raman data and neighboring orbital model analysis reveal that the two optical absorption bands correspond to charge transfers from aryl groups with different nodal structures in their pi orbitals. Copyright © 2012 John Wiley & Sons, Ltd. The three-chromophore cation (left) has a symmetric charge distribution in its ground state and three equivalent charge-bearing units in its lowest excited state. Coupling between the three units occurs through the central nitrogen and pair-wise through the oxygen. The effects of the coupling on the electronic and resonance Raman spectra are interpreted using the neighboring orbital model.
    Print ISSN: 0894-3230
    Electronic ISSN: 1099-1395
    Topics: Chemistry and Pharmacology , Physics
    Published by Wiley
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  • 6
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    Perinuclear positioning of the inactive human cystic fibrosis gene depends on CTCF, A-type lamins and an active histone deacetylase (2012)
    Wiley
    Details
    Publication Date: 2012-04-16
    Description: The nuclear positioning of mammalian genes often correlates with their functional state. For instance, the human cystic fibrosis transmembrane conductance regulator (CFTR) gene associates with the nuclear periphery in its inactive state, but occupies interior positions when active. It is not understood how nuclear gene positioning is determined. Here, we investigated trichostatin A (TSA)-induced repositioning of CFTR in order to address molecular mechanisms controlling gene positioning. Treatment with the histone deacetylase (HDAC) inhibitor TSA induced increased histone acetylation and CFTR repositioning towards the interior within 20 minutes. When CFTR localized in the nuclear interior (either after TSA treatment or when the gene was active) consistent histone H3 hyperacetylation was observed at a CTCF site close to the CFTR promoter. Knockdown experiments revealed that CTCF was essential for perinuclear CFTR positioning and both, CTCF knockdown as well as TSA treatment had similar and CFTR-specific effects on radial positioning. Furthermore, knockdown experiments revealed that also A-type lamins were required for the perinuclear positioning of CFTR. Together, the results showed that CTCF, A-type lamins and an active HDAC were essential for perinuclear positioning of CFTR and these components acted on a CTCF site adjacent to the CFTR promoter. The results are consistent with the idea that CTCF bound close to the CFTR promoter, A-type lamins and an active HDAC form a complex at the nuclear periphery, which becomes disrupted upon inhibition of the HDAC, leading to the observed release of CFTR. J. Cell. Biochem. © 2012 Wiley Periodicals, Inc.
    Electronic ISSN: 0091-7419
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Published by Wiley
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  • 7
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    Excited state mixed valence in a dual-bridged three-chromophore system (2012)
    Wiley
    Details
    Publication Date: 2012-01-27
    Description: The optical and resonance Raman spectra of the 2,2′: 6′,2″:6″,6-trioxytriphenyl-amine cation are measured and interpreted. This molecule contains two simultaneous types of coupling between three chromophores and two types of bridging atoms. The first and conventional coupling involves a single nitrogen bridge that couples all three aryl groups. The second is provided by the three oxygen atoms, each of which bridges two adjacent aryl groups. There are two bands in the visible region of the optical absorption spectrum; their assignment and the interpretation of the contributing orbitals and electronic states are described in terms of the neighboring orbital model that explains the effects of the two types of coupling. The bonding changes that take place in the excited electronic states are probed by resonance Raman spectroscopy intensities and analyzed using the time-dependent theory of resonance Raman spectroscopy. The optical absorption spectrum was fit using the measured vibrational frequencies and excited state distortions. The distortions correlate well with the bonding changes predicted by the neighboring orbital model. The resonance Raman data and neighboring orbital model analysis reveal that the two optical absorption bands correspond to charge transfers from aryl groups with different nodal structures in their pi orbitals. Copyright © 2012 John Wiley & Sons, Ltd. The three-chromophore cation (left) has a symmetric charge distribution in its ground state and three equivalent charge-bearing units in its lowest excited state. Coupling between the three units occurs through the central nitrogen and pair-wise through the oxygen. The effects of the coupling on the electronic and resonance Raman spectra are interpreted using the neighboring orbital model.
    Print ISSN: 0894-3230
    Electronic ISSN: 1099-1395
    Topics: Chemistry and Pharmacology , Physics
    Published by Wiley
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  • 8
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    Stochastic temporal disaggregation of monthly precipitation for regional gridded data sets (2014)
    Wiley
    Details
    Publication Date: 2014-10-10
    Description: Weather generators are used for spatio-temporal downscaling of climate model outputs (e.g., precipitation and temperature) to investigate the impact of climate change on the hydrological cycle. In this study, a multiplicative random cascade model is proposed for the stochastic temporal disaggregation of monthly to daily precipitation fields, which is designed to be applicable to grids of any spatial resolution and extent. The proposed method uses stationary distribution functions that describe the partitioning of precipitation throughout multiple temporal scales (e.g., weekly and bi-weekly scale). Moreover, it explicitly considers the intensity and spatial covariance of precipitation in the disaggregation procedure, but requires no assumption about the temporal relationship and spatial isotropy of precipitation fields. A split sampling test is conducted on a high-resolution (i.e., 4×4 km 2 grid) daily precipitation data set over Germany (≈ 357 000 km 2 ) to assess the performance of the proposed method during future periods. The proposed method has proven to consistently reproduce distinctive location dependent precipitation distribution functions with biases less than 5% during both a calibration and evaluation period. Furthermore, extreme precipitation amounts and the spatial and temporal covariance of the generated fields are comparable to those of the observations. Consequently, the proposed temporal disaggregation approach satisfies the minimum conditions for a precipitation generator aiming at the assessment of hydrological response to climate change at regional and continental scales or for generating seamless predictions of hydrological variables.
    Print ISSN: 0043-1397
    Electronic ISSN: 1944-7973
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 9
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    Drug Release from Three-Dimensional Cubic Mesoporous Silica Nanoparticles Controlled by Nanoimpellers (2014)
    Wiley
    Details
    Publication Date: 2014-01-10
    Description: Mesoporous silica nanoparticles with a cubic ( Ia 3 d ) pore structure are derivatized with light-activated nanoimpellers to control the release of loaded guest molecules under external photo-control. The nanoimpellers consist of azobenzene derivatives that are attached to the interiors of the three-dimensional interconnected pores, and undergo photoisomerization that results in dynamic wagging motions of the unbound termini and drives the expulsion of molecules from the pores. Stimulated release experiments monitored by fluorescence spectroscopy demonstrate that the nanoimpeller-functionalized MCM-48 particles are able to trap and release both hydrophilic and hydrophobic cargo molecules under external photocontrol in aqueous, non-aqueous, and intracellular environments.
    Print ISSN: 0044-2313
    Electronic ISSN: 1521-3749
    Topics: Chemistry and Pharmacology
    Published by Wiley
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  • 10
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    Load Risks of Subsoil Compaction and Depths of Stress Propagation in Arable Luvisols (2010)
    Wiley
    Details
    Publication Date: 2010-09-01
    Print ISSN: 0361-5995
    Electronic ISSN: 1435-0661
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Wiley
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