Angular dependence of the polarization of the recoil proton from the reaction γp→π0 p in the region of the second resonance

The polarization of the recoil proton from the reactionγp→π ⁰ p has been measured for photon energies between 600 and 1,200 MeV and pion c.m. angles between 90° and 150°.     

Selective internuclear coupling estimation in the solid-state NMR of multiple-spin systems

A new solid-state NMR method is presented for estimating homonuclear dipole-dipole couplings for selected groups of nuclear spins in a multiple-spin coupled network. The methodology combines off-magic-angle spinning, frequency selective spin echoes, and multiple quantum filtering. The new method is insensitive to incoherent relaxation effects and may be used to estimate weak couplings. Internuclear (13)C-(13)C couplings are estimated in uniformly (13)C-labelled l-Histidine·HCl·H(2)O. Weak intermolecular couplings between (13)C nuclei separated by distances exceeding 6 ? are estimated.     

Polymeric surfactants from styrene‐co‐maleic‐anhydride copolymers

Polymeric surfactants are usually prepared via copolymerisation of suitably substituted monomers. In this study, polymer surfactants were made by modifying a highly functionalized polymer chain back bone: a copolymer of styrene and maleic anhydride, SMA (34wt.‐% MA), was turned into anionic, cationic and nonionic surfactants by saponification and imidation of the MA functions. In some cases, the chains were partly hydrophobized by stearyl substituents. All surfactants were water soluble without forming hydrogels. To different degrees, they proved themselves as dispersants and thickeners. Carbon black and titanium dioxide were excellently dispersed by the ionic derivatives of SMA while latices were particularly well thickened by hydrophobized nonionic derivatives.     

Backward electroproduction of π+ mesons in the second and third nucleon resonance region

The reactionep→enπ ⁺ has been studied in the invariant mass range of 1.44≦W≦1.83 GeV. The outgoing pion was detected in the backward direction (cosλ _π ^* ≦-0.94) with respect to the virtual photon at four-momentum transfers of 0.4≦q ²≦0.7 (GeV/c)². The values of the helicity-1/2-partial wave amplitudesA _2?(D ₁₃(1520)) andA _3?(F ₁₅(1688)) were determined by a phenomenological analysis and compared with single quark transition models (S.Q.T.M.).     

Neutron-induced production of protons, deuterons and tritons on copper and bismuth

Inclusive cross sections for production of protons, deuterons and tritons by neutrons in the energy range of 300–580 MeV on copper and bismuth have been measured at five angles between 54° and 164°. The systematic dependence of the invariant cross sections on incident energy and emission angle are evaluated. For the study of the mass-number dependence earlier data on carbon are included. The results are discussed on the basis of different models, like quasi-two-body sealing or moving-source model.     

Modeling the solidification process in mortar due to internal mass exchange

Aim of the investigation is to model phase transition processes induced by mass transfer in multi-phase and multi-species mixtures. More specific, the innovative concept of using Superabsorbent Polymers (SAPs) as additives in grouting mortars represents a promising practical application, e. g. in mechanized tunneling. In this contribution, we focus on both the driving force for mass transfer as well as the kinetics for water migration, whereas an extension to the classical Theory of Porous Media (TPM) provides a reasonable modeling framework. As a result, the gelation process of the mixture can be described with respect to time. (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

THE PHOTOCHEMISTRY OF 3-NITROBENZOYL AND 4-NITROBENZOYL AZIDES: POSSIBLE REAGENTS FOR PHOTOAFFINITY LABELING

Abstract— The photochemistry of 3- and 4-nitrobenzoyl azides was studied to examine their suitability for use in photolabeling procedures. These aroyl azides absorb light in the near UV-spectral region. Their irradiation leads both to photo-Curtius rearrangement with formation of the analogous isocyan-ates and to generation of nitrenes by loss of nitrogen. The chemical and spectroscopic properties of the aroyl nitrenes indicate that they are singlets in their ground states. These singlet nitrenes insert rapidly into unactivated, aliphatic carbon-hydrogen bonds, trap nucleophiles, and add to olefins to form aziridines with retention of stereochemistry. Photolabeling agents based on these azides may offer some advantages over conventional agents for the labeling of lipophilic sites.     

Electroproduction of π+ mesons at forward and backward direction in the region of theD 13(1520) andF 15(1688) resonances

We report on measurements of the reactionep→enπ⁺ in the region of theD ₁₃(1520) andF ₁₅(1688) resonances. At an invariant four-momentum transferq ²=0.3 (GeV/c)² the outgoing pion was detected in the forward and backward directions. The values of the helicity-1/2-partial wave amplitudesA _2?(D ₁₃(1520)) andA _3?(F ₁₅(1688)) are determined from these measurements. A comparison of the results with single quark transition models is made.     

Search for the density effect in inner-shell lonization by ultra relativistic electron impact

We have extended the measurements ofK-andL-shell ionization cross sections by electron impact into the ultra relativistic energy region, 0.9≦E≦2.0 GeV, in order to search for a saturation of the cross section. This phenomenon, which is due to the polarization of the target medium, is called density effect. It is predicted to occur at several hundred MeV impact energy and preferentially for lowZ target elements. Theoretical calculations are presented, based on the one-photon-exchange approximation. The absolute measurements of theK-andL-shell cross sections for Ni(K), Cu(K), Ag(K, L) and Au(L) performed at the 2.5 GeV electron synchrotron of the Bonn University, however, exhibit that the cross sections show no saturation but are still increasing. Furthermore, from theK X-ray yields, obtained at 0.9 and 2.0 GeV by bombarding the lowZ elements S, Ca, Mn, Ni and Ge, we obtain for the corresponding cross section ratio σ _K (2GeV)/σ _K (0.9GeV)=1.08±0.01 on the average. TheK X-ray yield of a composite Ca — Mn target amounts to $$[\sigma _K (Ca;2.0GeV)/\sigma _K (Mn;2.0GeV)]/[\sigma _K (Ca;0.9GeV/\sigma _K (Mn;0.9GeV)] = 0.99 \pm 0.02.$$ . All three results are in disagreement with theory. This severe discrepancy is discussed but the origin for it is not yet understood.