Double-hadron leptoproduction in the nuclear medium

The first measurements of double-hadron production in deep-inelastic scattering within the nuclear medium were made with the HERMES spectrometer at DESY HERA using a 27.6 GeV positron beam. By comparing data for deuterium, nitrogen, krypton, and xenon nuclei, the influence of the nuclear medium on the ratio of double-hadron to single-hadron yields was investigated. Nuclear effects on the additional hadron are clearly observed, but with little or no difference among nitrogen, krypton, or xenon, and with smaller magnitude than effects seen on previously measured single-hadron multiplicities. The data are compared with models based on partonic energy loss or prehadronic scattering and with a model based on a purely absorptive treatment of the final-state interactions. Thus, the double-hadron ratio provides an additional tool for studying modifications of hadronization in nuclear matter.     

A Double‐Armed,Hydrophilic Transition Metal Complex as a Paramagnetic NMR Probe

Synthetic metal complexes can be used as paramagnetic probes for the study of proteins and protein complexes. Herein, two transition metal NMR probes (TraNPs) are reported. TraNPs are attached through two arms to a protein to generate a pseudocontact shift (PCS) using cobalt(II), or paramagnetic relaxation enhancement (PRE) with manganese(II). The PCS analysis of TraNPs attached to three different proteins shows that the size of the anisotropic component of the magnetic susceptibility depends on the probe surroundings at the surface of the protein, contrary to what is observed for lanthanoid‐based probes. The observed PCS are relatively small, making cobalt‐based probes suitable for localized studies, such as of an active site. The obtained PREs are stronger than those obtained with nitroxide spin labels and the possibility to generate both PCS and PRE offers advantages. The properties of TraNPs in comparison with other cobalt‐based probes are discussed.     

High-resolution investigation of the 112Sn(p,p')112Sn reaction

The ¹¹²Sn(p, p') reaction was studied at proton energies of 20.51 and 25.0 MeV. The outgoing protons were momentum analysed with an Enge split-pole spectrograph and recorded with position-sensitive solid-state detectors with a total resolution between 10 and 15 keV. Excitation energies and angular distributions for states below 5.5 MeV excitation energy were obtained. The angular distributions were compared with macroscopic DWBA calculations in order to extract L-values and deformation parameters. Coupled-channels calculations were performed to investigate two-phonon excitations and the mixing between one- and two-phonon states. The results of the present experiment are compared with previous experimental results and with number-projected BCS calculations. The results for some of the excited states were compared with similar results for the other even Sn isotopes.     

Flavor decomposition of the sea-quark helicity distributions in the nucleon from semiinclusive deep inelastic scattering

Double-spin asymmetries of semiinclusive cross sections for the production of identified pions and kaons have been measured in deep inelastic scattering of polarized positrons on a polarized deuterium target. Five helicity distributions including those for three sea quark flavors were extracted from these data together with reanalyzed previous data for identified pions from a hydrogen target. These distributions are consistent with zero for all three sea flavors. A recently predicted flavor asymmetry in the polarization of the light quark sea appears to be disfavored by the data.     

ENDOR spectroscopy at 275 GHz

A pulsed ENDOR spectrometer operating at a microwave frequency of 275 GHz is described. The results demonstrate that this type of spectroscopy can now be performed routinely at this high microwave frequency. The advantages compared to conventional EPR frequencies are the high spectral resolution, time resolution, and sensitivity.     

A finite basis theorem for quasivarieties

We consider varieties with the property that the intersection of any pair of principal congruences is finitely generated, and, in fact, generated by pairs of terms constructed from the generators of the principal components in a uniform way. We say that varieties with this property haveequationally definable principal meets (EDPM). There are many examples of these varieties occurring in the literature, especially in connection with metalogical investigations. The main result of this paper is that every finite, subdirectly irreducible member of a variety with EDPM generates a finitely based quasivariety. This is proved in Section 2. In the first section we prove that every variety with EDPM is congruence-distributive.Presented by George Gratzer.     

Contribution of 2h̷ω transitions to the excitation of 0+ states in 58Ni and 26Mg in inelastic electron scattering

The excitation of 0⁺ states in ⁵⁸Ni and ²⁶Mg has been investigated by inelastic electron scattering. Shell model calculations in a 1&?;ω model space are not able to reproduce the data, which clearly show contributions from 2&?;ω, i.e. giant monopole resonance-like, excitations.