Investigation of the superstructure of native collagen by a combination of small angle X-ray scattering,electron microscopy and light diffraction

Summary It is shown that there exists a direct correlation between the light diffraction pattern of an electron-microscopical picture and the X-ray small angle scattering. By this means it can be proved for native collagen prepared by a special method that the density pattern of stained samples imaged in the electron microscopy is identical with the density pattern available from moist fibres. The reflex intensities of the small angle X-ray scattering are taken for calculating the density structure whereby the necessary phases are delivered by the electron microscopic examination combined with light diffraction.

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Zusammenfassung Zwischen der Lichtbeugung an elektronenmikroskopischen Bildern und der Röntgenkleinwinkelstreuung wird die direkte Korrespondenz aufgezeigt. Hierbei kann erwiesen werden, daß das elektronenmikroskopische Bild von speziell präpariertem, nativem Kollagen jene Dichtestruktur widerspiegelt, welche auch im feuchten Zustand vorliegt.Aus den Intensitäten der Röntgenbeugung wird die Elektronendichteverteilung errechnet. Die hierzu erforderlichen Phasen können über die Lichtbeugung aus dem elektronenmikroskopischen Bild entnommen werden.

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With 17 figures     

Thermomechanics of elastic systems on simple elongation

Summary It is shown by means of isobaric simple elongation experiments on natural rubber and a quasi-isotropic steel wire that the dynamical internal properties in these elastic systems have to be changed. Their contributions are related to the thermal expansion coefficient > 0, thus, always yielding a cooling of adiabatically strained samples. These changes of the internal properties are predominant at small strains only observable from the energy balance during the deformation process. The thermodynamical origins of this thermo-elastical effect may be related to a general saturation condition derived from the appropriate Gibbs-function. With the aid of equations from the mechanical state functions, calculations can be fitted to the experiments using the known thermo-mechanical properties of the systems investigated.

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Zusammenfassung Die thermomechanische Beschreibung uniaxial verstreckten Naturgummis und quasi-isotropen Stahldrahtes weist die Bedeutung der Änderung der inneren Eigenschaften sichtbar nach, insbesondere bei kleinen Deformationen. Diese Beiträge sind mit dem isothermen Ausdehnungskoeffizient der isotropen Probe verknüpft, so daß zu Beginn der Deformation stets eine adiabatische Abkühlung der Systeme erfolgen muß. Die Änderung der inneren Eigenschaften kann thermodynamisch als Sättigung interpretiert werden (im Falle des Gummis als leerstellengesättigte elastische Flüssigkeit, im Falle des Stahls als phononengesättigter Festkörper). Die Beschreibung erfolgt mit Hilfe einer geeigneten Gibbs-Funktion. Experimentelle Resultate können unter Ausnutzung der bekannten thermodynamischen Koeffizienten vollständig beschrieben werden.

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With 5 figures     

Total and differential cross-sections for the pp\rightarrow pp\eta^\prime reaction near threshold

The -meson production in the reaction has been studied at excess energies of Q = 26.5, 32.5 and 46.6 MeV using the internal beam facility COSY-11 at the cooler synchrotron COSY. The total cross-sections as well as one angular distribution for the highest Q-value are presented. The excitation function of the near-threshold data can be described by a pure s-wave phase space distribution with the inclusion of the proton-proton final-state interaction and Coulomb effects. The obtained angular distribution of the -mesons is also consistent with pure s-wave production.Received: 11 August 2003, Revised: 14 November 2003, Published online: 6 April 2004PACS: 13.60.Le Meson production - 13.75.-n Hadron-induced low- and intermediate-energy reactions and scattering (energy GeV) - 13.85.Lg Total cross-sections - 25.40.-h Nucleon-induced reactions     

Eta physics at threshold

The production of - and -mesons in elementary nucleon-nucleon collisions has been investigated at the synchrotrons CELSIUS, COSY and SATURNE. The high-quality proton beam with low emittance and small momentum spread permits to study the creation of these mesons very close to the kinematical threshold, where --due to the rapid growth of the phase space volume-- the total cross-section increases by orders of magnitude over a few MeV range of the excess energy. The magnitude and energy dependence of the total cross-section as well as the occupation distribution of the phase space serve as observables for investigating the mechanisms underlying the production processes and the interaction of mesons with nucleons. The precise data on the and creation via the reactions allowed to settle the general features of the - and -meson production and revealed the sensitivity of the mentioned observables to the nucleon-nucleon-meson final-state interaction. The particular production properties, like for example, the determination of the dominating exchange processes which lead to the excitation of the S ₁₁ nucleon isobar in the case of creation, must be established by confrontation with other observables. The present status of this investigation with an emphasis on the results of the COSY-11 Collaboration is briefly presented. The available data are interpreted in view of the production mechanism and the meson-nucleon interaction.Received: 30 September 2002, Published online: 22 October 2003PACS: 13.60.Le Meson production - 13.75.-n Hadron-induced low- and intermediate-energy reactions and scattering (energy GeV) - 13.85.Lg Total cross sections - 25.40.-h Nucleon-induced reactions     

Detection of anisotropic hyperfine transitions in zero magnetic field using field-cycling techniques

For the first time, we describe the detection of hyperfine transitions in zero magnetic field using field-cycling techniques and pulsed EPR spectroscopy. The sample investigated was coal, which shows an anisotropic electron spin-(13)C hyperfine interaction.     

Linear Response Equilibrium versus echo-planar encoding for fast high-spatial resolution 3D chemical shift imaging

In this work Linear Response Equilibrium (LRE) and Echo-planar spectroscopic imaging (EPSI) are compared in terms of sensitivity per unit time and power deposition. In addition an extended dual repetition time scheme to generate broad stopbands for improved inherent water suppression in LRE is presented. The feasibility of LRE and EPSI for assessing cholesterol esters in human carotid plaques with high spatial resolution of 1.95×1.15×1.15 mm(3) on a clinical 3T MR system is demonstrated. In simulations and phantom experiments it is shown that LRE has comparable but lower sensitivity per unit time relative to EPSI despite stronger signal generated. This relates to the lower sampling efficiency in LRE relative to EPSI as a result of limited gradient performance on clinical MR systems. At the same time, power deposition of LRE is significantly reduced compared to EPSI making it an interesting niche application for in vivo high field spectroscopic imaging of metabolites within a limited bandwidth.     

Weierstrass points on X 0(p ℓ) and arithmetic properties of Fourier coefficients of cusp forms

Generally it is unknown, whether or not ∞ is a Weierstrass point on the modular curve X ₀(N) if N is squarefree. A classical result of Atkin and Ogg states that ∞ is not a Weierstrass point on X ₀(N), if N=pM with p prime, p ∤ M and the genus of X ₀(M) zero. We use results of Kohnen and Weissauer to show that there is a connection between this question and the p-adic valuation of cusp forms under the Atkin–Lehner involution. This gives, in a sense, a generalization of Ogg’s Theorem in some cases.      

1,2-diphosphaacenaphthene 1,2-dications: synthetic, stereochemical and computational study of the stabilising role of naphthalene-1,8-diyl backbone

Syntheses and full characterisation data (including single crystal diffraction) of three 1,2‐diphosphonium dicationic species with the naphthalene‐1,8‐diyl (Nap) backbone are reported. The oxidation of Nap[P(NMe₂)₂]₂ with P₂I₄ to its 1,2‐dication was achieved. meso‐ and rac‐forms of “all carbon” 1,2‐diphosphonium dications were obtained in good yields and purity by double alkylation of the parent diphosphine (1,2‐diphenyl‐1,2‐diphosphaacenaphthene) with methyl triflate or trimethyloxonium tetrafluoroborate. Each methylating reagent produces one of the rac‐ or meso‐forms of the dication diastereospecifically. Structural parameters of the new dications are discussed with respect to other phosphorus 1,2‐dications. DFT (B3LYP) computations revealed the significant role of the naphthalene backbone in stabilisation of the dicationic motif and helped to assess the energy cost of the steric clash of a variety of groups attached to the peri‐positions of naphthalene. The synthesis and single crystal X‐ray data of the extremely crowded Nap[P(?Se)(OiPr)₂]₂ are discussed, and are contrasted with the unsuccessful synthesis of Nap(PtBu₂)₂ from NapLi₂ and ClPtBu₂.