The (d,t) and (d,t) reactions on 18O and the 1p spin-orbit splitting

The reactions ¹⁸O(d, t)¹⁷O and ¹⁸O(d, τ)¹⁷N have been investigated at ifE_{d = 52 MeV}. Energy spectra of tritons and τ particles have been measured up to excitation energies of 25 MeV in ¹⁷O and 12 MeV ¹⁷N, respectively, and spectroscopic factors have been obtained by a DWBA analysis of the measured angular distributions. From a comparison of the t-and τ-spectra the distribution of $\text{T =}\text{1}\text{2}\text{and}\text{3}\text{2}$ spectroscopic strengths in ¹⁷O could be deduced and analog relations between $\text{T =}\text{3}\text{2}$ states in ¹⁷N and ¹⁷O could be established. Nearly the total $\text{T =}\text{3}\text{2}$ strengths of the $\text{1}\text{p}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{and}\text{1}\text{p}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$ shells and nearly the complete $\text{T =}\text{1}\text{2}$ strength of the $\text{1}\text{p}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ shell have been found, whereas only one third of the $\text{T =}\text{1}\text{2}$ strength of the $\text{1}\text{p}\text{3}\text{2}$. Shell could be clearly identified. The observed centroid energies are understood from the different $\text{1}\text{d}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}$$\text{1}\text{p}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}{}^{\mathrm{?}}\text{1)}$ and $\text{1}\text{d}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}$ effective residual interactions. This supports a strong isospin dependence of the 1p spin-orbit splitting.     

Monte Carlo based electronic structure techniques: analysis and applications

Monte Carlo based variational electronic structure techniques are examined. The nature of the convergence of such methods, associated extrapolation methods and techniques for wavefunction optimization are discussed. These techniques are illustrated with an application to the H⁺₃ system. Compact and accurate correlated wavefunctions for this system are reported.     

Energieumsetzung in Wärme beim kritischen Bruchbeginn in PMMA

Zusammenfassung Anhand von Ergebnissen experimenteller Untersuchungen wird gezeigt, daß in PMMA-Materialien verschiedenen Molekulargewichtes die für den kritischen Bruchbeginn geleistete Arbeit — ähnlich wie bei der Kaltverstreckung — hauptsächlich in Wärme umgesetzt wird. Hervorgerufen wird die Wärme durch Reibungseffekte der Molekülbündel im mikroskopisch kleinen Bereich an der Rißspitze, der Craze-Zone. Die dort auftretenden Temperaturerhöhungen werden diskutiert.

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Summary By experimental results it is shown that at the onset of critical fracture in polymethylmethacrylate materials of different molecular weights the strain energy release rate is mainly turned into heat; this result corresponds to that of the macroscopic deformation-process in other polymers. The heat is generated in the craze zone at the crack tip by friction of the molecule bundles. The maximum temperature rises are discussed.

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Mit 6 Abbildungen and 2 Tabellen     

Loops on loops: generation of complex scaffolded peptides presenting multiple cyclic fragments

Scaffolded peptides presenting two different cyclic peptide fragments through a cyclic peptidomimetic scaffold in a site-selective fashion, were generated by stepwise solid phase synthesis and fragment condensation in parallel, demonstrating that either strategy is adequate to generate complex scaffolded peptides.     

Electronic and magnetic properties of a hexanuclear ferric wheel

The electronic and magnetic properties of the hexanuclear ferric wheel [ LiFe6(OCH3)12-(dbm)6] PF6 have been studied with all-electron Hartree-Fock and full-potential density functional calculations. The best agreement for the magnetic exchange coupling is at the level of the B3LYP hybrid functional. Surprisingly, the Hartree-Fock approximation gives the wrong sign for the exchange coupling. The local density approximation and the gradient corrected functional PBE strongly overestimate the exchange coupling due to the too large delocalization of the d-orbitals. These findings are supported by results from the Mulliken population analysis for the magnetic moments and the charge on the individual atoms.     

High energy proton emission in reactions induced by 315 MeV 16O ions

Inclusive proton spectra have been measured for the reaction ¹⁹⁷Au(¹⁶O, p)X at 315 MeV. The data, which are consistent with emission from a moving source, are compared with the fireball model and with models preequilibrium emission.     

Theoretical studies of surface diffusion: Self-diffusion in the bcc (211) system

Surface self-diffusion in the bcc (211) system is studied using numerical molecular dynamics simulations. Calculations based on Lennard-Jones pair potentials extracted from fits to bulk thermodynamic data produce self-diffusion constants in excellent agreement with available experimental data. These same potentials have been shown previously to yield similar agreement with experimental self-diffusion data for the bcc (110) system.