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  • 1
    Electronic Resource
    Electronic Resource
    Small-angle neutron scattering from bacterial magnetite (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 4475-4477 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Small-angle neutron scattering was used to study the magnetic properties of intracellular magnetite crystals (magnetosomes) in the bacterium, Aquaspirillum magnetotacticum, grown in pure culture. An average of 20 single-domain magnetite (Fe3O4) particles of diameter 400–500 A(ring) are arranged in a chain that longitudinally traverses each cell. The net magnetic dipole moment carried by each chain is sufficient to orient the bacterium in the geomagnetic field. A contrast variation series, performed on a nonmagnetic variant, established that a 30% D2O/H2O ratio in the suspension buffer resulted in the minimization of the scattering from the bacterium itself, thereby enhancing that from the magnetosomes. Measurements of A. magnetotacticum in 30% D2O and an applied field of 25 G confirmed that the scattering from the magnetite particles in bacteria grown under iron-rich conditions is of ferromagnetic character, while that from magnetosomes in bacteria grown under iron-starved conditions is characteristic of superparamagnetic particles. In both cases, the wave-vector dependence of the scattering can be represented by a sum of Lorentzian plus Lorentzian squared terms, from which longitudinal as well as transverse spin correlation lengths were extracted. The results describe dynamic spin correlation lengths on the order of 50 A(ring), which are superposed on the static magnetosome cluster.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.344886
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  • 2
    Electronic Resource
    Electronic Resource
    Stray-light correction in photoacoustic measurements of solid samples (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 62 (1987), S. 55-61 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An experimental correction procedure is presented which allows one to measure separately and to eliminate signal contributions produced at the walls of photoacoustic cells by the directly incident light or by the light (diffusively) reflected from the solid sample. This stray-light correction procedure is tested for an opaque and a transparent photoacoustic cell. It helps to reduce the systematic error of photoacoustic measurements considerably when the solid to be analyzed and the reference material have different reflection properties and when in quantitative thermal depth profiling a larger interval for the modulation frequency of heating is needed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.339160
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  • 3
    Electronic Resource
    Electronic Resource
    Extending the Angular Range of Neutron Reflectivity Measurements from Planar Lipid Bilayers: Application to a Model Biological Membrane (1995)
    s.l. : American Chemical Society
    Langmuir 11 (1995), S. 3218-3222 
    Details
    ISSN: 1520-5827
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/la00008a055
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  • 4
    Electronic Resource
    Electronic Resource
    Excitation energy transfer of a bichromophoric cross-shaped molecule investigated by polarized fluorescence spectroscopy (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 112 (2000), S. 9822-9827 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The excitation energy transfer (EET) of a bichromophoric cross-shaped molecule was investigated by stationary polarized fluorescence spectroscopy in the solid state. For this purpose 2,2′,7,7′-tetrakis(biphenyl-4-yl)-9,9′-spirobifluorene was embedded in a polymeric bisphenol-A-polycarbonate (PC) matrix. The dependence of the fluorescence on concentration and wavelength was determined. The role of the intermolecular and intramolecular EET is dealt with separately and discussed by means of the degree of polarization. The intermolecular excitation energy transfer is described in terms of a Förster transfer mechanism. The intramolecular transfer is prevented for the zero-point vibrational levels by the molecular cross-shaped structure, but is found for a wide range of wavelength, presumably based on vibrationally excited states. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.481620
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  • 5
    Electronic Resource
    Electronic Resource
    Mutations in the NOD2/CARD15 gene in Crohn's disease are associated with ileocecal resection and are a risk factor for reoperation (2004)
    Oxford, UK : Blackwell Science Ltd
    Alimentary pharmacology & therapeutics 19 (2004), S. 0 
    Details
    ISSN: 1365-2036
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Background : Mutations within the NOD2/CARD15 gene have recently been shown to be associated with Crohn's disease.Aims : To investigate the clinical impact of the three common NOD2/CARD15 mutations in patients with Crohn's disease.Methods : We investigated the prevalence of the three common NOD2/CARD15 mutations (Arg702Trp, Gly908Arg, 3020insC) in 180 patients with Crohn's disease, 70 patients with ulcerative colitis and 97 controls. In patients with Crohn's disease, prevalence of NOD2/CARD15 mutations were correlated to clinical and demographical parameters.Results : In Crohn's disease patients, 35.6% carried at least one mutant allele of NOD2/CARD15 mutations compared with 14.3% of patients with ulcerative colitis (P = 0.006) and to 15.5% of controls (P = 0.0001). Genotype phenotype analyses revealed that NOD2/CARD15 mutations determined younger age at disease diagnosis (P = 0.03), ileal disease location (P = 0.01) and ileocecal resections (P = 0.0002). Interestingly, reoperation with resection of the anastomosis was significantly more frequent in patients with NOD2/CARD15 mutations (P = 0.01).Conclusions : Our investigations support the current hypothesis that NOD2/CARD15 mutations are associated with a phenotype of Crohn's disease with younger age at diagnosis, ileal involvement, ileocecal resections and a high risk of postoperative relapse and reoperation. NOD2/CARD15 mutations might therefore be used to identify high risk patients for relapse prevention strategies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2036.2004.01967.x
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  • 6
    Electronic Resource
    Electronic Resource
    Multiple small-angle neutron scattering characterization of the densification of ceramics: application to microporous silica (1989)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 22 (1989), S. 539-545 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Multiple small-angle neutron scattering was used to characterize the microstructure evolution of porous silica as a function of thermal processing. This new technique offers a statistically significant determination of microstructure morphology in the 0.08–10 μm range, which was previously inaccessible without increasing the resolution of the currently available scattering spectroscopy beamlines. All of the scatterers, which in the present work are pores within ceramic bodies, are measured whether they are open or closed. Earlier mercury porosimetry and nitrogen desorption measurements of the microporous silica system indicated that there are two major populations of pores in this material, differing in pore size by approximately an order of magnitude. In this work, it was found that densification during the intermediate stages of sintering is accompanied by coarsening to radii 〉 0.22 μm within the population of large pores in microporous silica. In the late stages of sintering, there are no detectable pores with radii 〉 0.08 μm, and radii of gyration equal to 33 and 28 nm were measured. Finally, Monte Carlo simulations were carried out to complement the neutron-scattering measurements, to predict the influence on the results of the bimodal distribution, and to explore the sensitivity of the multiple-scattering method.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889889007119
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  • 7
    Electronic Resource
    Electronic Resource
    Small-angle-scattering determination of the microstructure of porous silica precursor bodies (1990)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 23 (1990), S. 535-544 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Small-angle X-ray and small-angle neutron scattering measurements were carried out on a series of porous silica precursor (unsintered) bodies with different starting chemistries. The samples were prepared from mixtures containing 10 to 30 wt% colloidal silica sol and 90 to 70 wt% potassium silicate. Particle-size distributions were derived from the data using a maximum-entropy technique. Scattering data from the porous silica samples are especially suitable for such an analysis because the colloidal particles and clusters and aggregates of these particles are verified in detail to be spherical, and the scattering instrument use for this study covered the entire range of sizes in this material and was very well calibrated. It was found that the lower the amount of colloidal silica, the broader the size distribution of the silica aggregates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889890008263
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  • 8
    Electronic Resource
    Electronic Resource
    The 30 m Small-Angle Neutron Scattering Instruments at the National Institute of Standards and Technology (1998)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 31 (1998), S. 430-445 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Two high-resolution, general-purpose, small-angle neutron scattering instruments have been constructed at the National Institute of Standards and Technology's Center for Neutron Research. The instruments are 30 m long and utilize mechanical velocity selectors, pinhole collimation and high-data-rate two-dimensional position-sensitive neutron detectors. The incident wavelength, wavelength resolution and effective length of the instruments are independently variable, under computer control, and provide considerable flexibility in optimizing beam intensity and resolution. The measurement range of the instruments extends from 0.0015 to 0.6 Å−1 in scattering wavevector, corresponding to structure in materials from 10 Å to nearly 4000 Å. The design and characteristics of the instruments, and their modes of operation, are described, and data are presented which demonstrate their performance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889897017020
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  • 9
    Electronic Resource
    Electronic Resource
    Characterization of the densification of alumina by multiple small-angle neutron scattering (1991)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 47 (1991), S. 282-290 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Multiple small-angle neutron scattering was used to follow the evolution of the pore-size distribution in α-Al2O3 through the intermediate and final stages of sintering. This new technique enables the study of microstructure in the 0.08–10 μm size regime, which is the size range of importance for many materials systems, without needing to increase the resolution of currently available small-angle scattering instruments. The microstructure evolution results indicate a nearly constant effective pore radius for the alumina throughout the intermediate sintering stage, ranging from 0.19 μm at 54% of theoretical density to 0.17 μm at 79% dense. As the alumina densifies further, there is a transition region after which the effective pore radius grows rapidly to ≥0.6 μm at 97.5% dense.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0108767391000570
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  • 10
    Electronic Resource
    Electronic Resource
    Small angle neutron scattering studies of structural characteristics of agarose gels
    Amsterdam : Elsevier
    Biophysical Chemistry 53 (1994), S. 85-94 
    Details
    ISSN: 0301-4622
    Keywords: Agarose ; Gels ; Neutron scattering
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0301-4622(94)00079-4
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