ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
Collection
Keywords
Publisher
Language
Years
  • 1
    Electronic Resource
    Electronic Resource
    High energy two-photon states in finite versus infinite polyenes (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 96 (1992), S. 6862-6867 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Optical nonlinearity in π-conjugated polyenes depends crucially on a single two-photon state that is located above the one-photon allowed exciton. In the case of the infinite polyene this single state should be thought of as a collection of states with very narrow bandwidth. The location of this two-photon state in the infinite polyene is of considerable interest. We present numerical data for finite chains and discuss in detail why extrapolation of finite chain data to obtain the energies of the high energy states in the infinite polyene requires considerable care. Based on upper and lower bounds that we put on the energy of the two-photon state in question, we predict it to be extremely close to the one-photon excition in the infinite chain limit. We present recent experimental data for a polydiacetylene that is consistent with our prediction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.462576
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Substrate effects on the structure of epitaxial PbTiO3 thin films prepared on MgO, LaAlO3, and SrTiO3 by metalorganic chemical-vapor deposition (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 2607-2622 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Epitaxial PbTiO3 films were prepared by metalorganic chemical-vapor deposition on MgO(001)-, SrTiO3(001)-, and LaAlO3(001)-oriented substrates. Four-circle x-ray diffraction, transmission electron microscopy, Rutherford backscattering (RBS) channeling, and optical waveguiding were performed to characterize the deposited films. Epitaxial, single-crystal films were obtained on all three substrate materials under the same growth conditions. However, the defect structure of the films, including grain tilting, threading dislocation density, and 90° domain formation, was strongly dependent on the choice of substrate material. Films grown on MgO(001) and LaAlO3(001) (pseudocubic indices) substrates are nominally c-axis oriented; however, the PbTiO3 grains in the film form a fourfold domain structure, with the grains tilted ∼0.6° and ∼0.7°, respectively, toward the [100] directions (cubic or pseudo-cubic) of the substrates. In addition, these films contain a significant volume fraction of 90°-domain (a-axis) structures with a critical thickness hc for domain formation below the detection level of our experiments (hc≥100 A(ring)). Together, these structural defects result in a low RBS channeling yield reduction. In contrast, films grown on SrTiO3(001) substrates showed no tilting of the c-axis grains and a minimum RBS channeling yield of as low as ∼3%. In addition, we observed that below a critical film thickness of hc∼1500 A(ring), 90° domain formation was completely suppressed resulting in a nearly perfect single-crystal structure.The refractive indices and optical birefringence of the films were measured as a function of wavelength using the film-prism coupling method. Both the ordinary and extraordinary refractive indices for films grown on MgO(001) and LaAlO3(001) were higher than that of single-crystal PbTiO3; however, the optical birefringence of films grown on MgO(001) was reduced from that of the bulk. For films grown on SrTiO3(001), the ordinary refractive index was very close to that of single-crystal PbTiO3. We correlate the refractive index values and the reduced birefringence to the degree of residual strain and the volume fraction of 90° domains in the samples, respectively. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360121
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    New hydrophilicity scale derived from high-performance liquid chromatography peptide retention data: correlation of predicted surface residues with antigenicity and x-ray-derived accessible sites (1986)
    s.l. : American Chemical Society
    Biochemistry 25 (1986), S. 5425-5432 
    Details
    ISSN: 1520-4995
    Source: ACS Legacy Archives
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/bi00367a013
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Growth of high quality single-domain single-crystal films of PbTiO3 (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 65 (1994), S. 1106-1108 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Single-crystal films of PbTiO3 have been deposited on (100) SrTiO3 substrates by metalorganic chemical vapor deposition. X-ray diffraction spectra and transmission electron microscopy images revealed that the development of 90° domains was directly related to the thickness of the film. Single-domain, single-crystal films were obtained for film thickness less than 150 nm. The minimum yields of the films in ion-channeling experiments were only 3 %, similar to that of a perfect single crystal. The ordinary refractive index of the film measured by optical waveguiding experiment was also the same as that of PbTiO3 single crystals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.112112
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    TDSIR phasing: direct use of phase-invariant distributions in macromolecular crystallography (1995)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 51 (1995), S. 535-542 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: A new strategy for employing three phase triples invariant estimates from Hauptman's single isomorphous replacement (SIR) and anomalous dispersion (SAS) joint probability distribution formulae is outlined which produces a single unique phase-invariant solution in the case where the positions of the heavy-atom scatterers is known. A similar but non-identical result is obtained for the phase invariants of a structure for which a molecular-replacement solution has been obtained. It is important to note that the values of the individual native/derivative phases can be determined directly from the probability distribution formulae without having to utilize the phase-invariant estimates in an active way. Elimination of the multisolution aspect of utilizing phase-invariant estimates should have important repercussions with regard to phasing macromolecular sets of derivatized data. Trial calculations based on experimentally measured 2.5 Å data for three derivatives of cytochrome c550 are encouraging. The average of the three SIR maps resolves a number of structural ambiguities seen in the published multiple isomorphous replacement (MIR) map obtained from eight derivatives.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0108767395000870
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    On integrating the techniques of direct methods with anomalous dispersion. III. Estimation of two-wavelength two-phase structure invariants (1994)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 50 (1994), S. 307-311 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: For diffraction data at two wavelengths from a crystal with anomalous scatterers, there are six types of two-phase structure invariants for Friedel pairs. Two of the six are single-wavelength invariants; the other four are mixed-wavelength invariants. It is shown that the latter can be estimated by a straightforward extension of results from the probabilistic direct-methods theory for the single-wavelength anomalous scattering case described in paper I [Hauptman (1982). Acta Cryst. A38, 632–641]. Statistical tests of the mixed-wavelength estimates are reported for small-molecule and macromolecular examples.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0108767393009778
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Globbic approximation in low-resolution direct-methods phasing (2000)
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 56 (2000), S. 1148-1155 
    Details
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Probabilistic direct-methods phasing theory, originally based on a uniform atomic distribution hypothesis, is shown to be adaptable to a non-uniform bulk-solvent-compensated globbic approximation for protein crystals at low resolution. The effective number ng of non-H protein atoms per polyatomic glob increases with decreasing resolution; low-resolution phases depend on the positions of only Ng = Na/ng globs rather than Na atoms. Test calculations were performed with measured structure-factor data and the refined structural parameters from a protein crystal with ∼10 000 non-H protein atoms per molecule and ∼60% solvent volume. Low-resolution data sets with dmin ranging from 15 to 5 Å gave ng = admin + b, with a = 1.0 Å−1 and b = −1.9 for the test case. Results of tangent-formula phase-estimation trials emphasize that completeness of the low-resolution data is critically important for probabilistic phasing.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0907444900008362
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    On `globbicity' of low-resolution protein structures (1999)
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 55 (1999), S. 230-237 
    Details
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Using Harker's [Harker (1953). Acta Cryst. 6, 731–736] idea of spherically averaged polyatomic groups or `globs' as the units of structure suitable for analyzing low-resolution diffraction data from protein crystals, `globbic' scattering factors have been calculated for main-chain peptide units and amino-acid side-chain groups to 3 Å resolution via Debye's [Debye (1915). Ann. Phys. (Leipzig), 46, 809–823] scattering formula. It is shown that the scattering factors are insensitive to intra-globbic conformational variation and can be approximated fairly well by a single-Gaussian formula, i.e. fg(s) = Zg exp(−1.7Zgs2), where s = (sinθ)/λ and Zg is the total electron count for the atoms of the glob. Phase errors due to the globbic approximation and their effect on electron-density maps at 3.5 Å resolution have been assessed via calculations for the crambin structure; this analysis indicates that the globbic scattering factors will be useful in efforts to develop procedures for direct-methods phasing of diffraction data to ∼3.5 Å resolution from protein crystals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0907444998008208
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Bulk-solvent correction in direct-methods phasing (2000)
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 56 (2000), S. 451-457 
    Details
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: It is shown that for crystals of large proteins at low diffraction resolution, with N ∼ 10 000 independent non-H protein atoms and dmin ∼ 8 Å, a simple bulk-solvent correction yields the Sayre equation in its classical form, F _{\bf h} = q \textstyle \sum_{\bf k} F_{\bf k} F _{{\bf h} - {\bf k}}. In the low-resolution protein case, the proportionality factor becomes q = 1/[(\langle \rho_P \rangle - \rho_{S })V] , where V is the unit-cell volume, ρS is the assumed constant electron density in the solvent regions of the crystal and 〈ρP〉 is the average electron density in the protein regions. The classical form of the tangent formula follows from the bulk-solvent-corrected Sayre equation and its validity at low resolution is verified in empirical calculations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0907444900000573
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    Use of 'random-atom" phasing models to determine macromolecular heavy-atom replacement positions (1995)
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 51 (1995), S. 1020-1024 
    Details
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: A procedure is described by which the phase-invariant translation function may be used to provide starting set phases for the minimal function that are significantly better than those generated from random-atom coordinates. Applications to determine the heavy-atom positions for single isomorphous replacement data from macromolecular structures are very encouraging. In the case of chiral space groups, e.g. P41212 versus P43212, unlike Patterson functions, these methods provide the correct enantiomorph coordinates for the heavy-atom sites for whichever space group is chosen.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0907444995006044
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...