Paul Scherrer Institute

About: Paul Scherrer Institute is a facility organization based out in Villigen, Switzerland. It is known for research contribution in the topics: Neutron & Large Hadron Collider. The organization has 9248 authors who have published 23984 publications receiving 890129 citations. The organization is also known as: PSI.

Current use and future potential of organometallic radiopharmaceuticals

Abstract: Contrary to common belief, organometallic compounds exhibit remarkable stability in aerobic and even diluted aqueous solutions. Technetium-sestamibi (Cardiolite) is one of the most prominent examples of this class of compounds routinely used in nuclear medicine. This review summarises the recent progress in labelling of biomolecules with organometallic complexes for diagnostic and therapeutic application in radiopharmacy and exemplifies in detail developments focussing on organometallic technetium- and rhenium-tricarbonyl technologies. The value of such technologies has been recognised and they have become a valuable alternative to common labelling methodologies. An increasing number of groups have started to employ an organometallic precursor for the purpose of radioactive labelling of various classes of biomolecules, and the advantages and limitations of this new technique are compared with those of other labelling methods. The synthetic access to appropriate precursors via double-ligand exchange or aqueous carbonyl kit preparation for routine application is described. Strategies and examples for the design of appropriate bifunctional chelating agents for the Tc/Re-tricarbonyl core are given. The functionalisation of biomolecules such as tracers for the central nervous system (dopaminergic and serotonergic), tumour affine peptides (somatostatin receptors, neuroreceptors) and tumour binding single-chain antibody fragments is summarised. Where possible and appropriate, the in vitro and in vivo results in respect of these examples are compared with those obtained with classical 99mTc/188Re(V)- and 111In-labelled analogues. The preclinical results show the in many ways superior characteristics of organometallic labelling techniques.

Cross sections for the production of residual nuclides by low- and medium-energy protons from the target elements c, n, o, mg, al, si, ca, ti, v, mn, fe, co, ni, cu, sr, y, zr, nb, ba and au

Abstract: Cross sections for residual nuclide production by p-induced reactions were measured from thresholds up to 2.6 GeV using accelerators at CERN/Geneve, IPN/Orsay, KFA/Julich, LANL/Los Alamos, LNS/Saclay, PSI/Villigen, TSL/Uppsala, LUC/Louvain La Neuve. The target elements C, N, O, Mg, Al, Si, Ca, Ti, V, Mn, Fe, Co, Ni, Cu, Sr, Y, Zr, Nb, Ba and Au were investigated. Residual nuclides were measured by X- and γ-spectrometry and by Accelerator Mass Spectrometry (AMS). The measured cross sections were corrected for interfering secondary particles in experiments with primary proton energies above 200 MeV. Our consistent database covers presently ca 550 nuclear reactions and contains nearly 15000 individual cross sections of which about 10000 are reported here for the first time. They provide a basis for model calculations of the production of cosmogenic nuclides in extraterrestrial matter by solar and galactic cosmic ray protons. They are of importance for many other applications in which medium energy nuclear reactions have to be considered ranging from astrophysics over space and environmental sciences to accelerator technology and accelerator-based nuclear waste transmutation and energy amplification. The experimental data are compared with theoretical ones based on calculations using an INC/E model in form of the HETC/KFA2 code and on the hybrid model of preequilibrium reactions in form of the AREL code.

Quantum magnetism in the paratacamite family: towards an ideal kagomé lattice.

Abstract: We report muon spin rotation measurements on the $S=1/2$ (${\mathrm{Cu}}^{2+}$) paratacamite ${\mathrm{Zn}}_{x}{\mathrm{Cu}}_{4\ensuremath{-}x}(\mathrm{OH}{)}_{6}{\mathrm{Cl}}_{2}$ family. Despite a Weiss temperature of $\ensuremath{\sim}\ensuremath{-}300\text{ }\text{ }\mathrm{K}$, the $x=1$ compound is found to have no transition to a magnetic frozen state down to 50 mK as theoretically expected for the kagom\'e Heisenberg antiferromagnet. We find that the limit between a dynamical and a partly frozen ground state occurs around $x=0.5$. For $x=1$, we discuss the relevance to a singlet picture.

Reaching the magnetic anisotropy limit of a 3d metal atom

Abstract: Designing systems with large magnetic anisotropy is critical to realize nanoscopic magnets. Thus far, the magnetic anisotropy energy per atom in single-molecule magnets and ferromagnetic films remains typically one to two orders of magnitude below the theoretical limit imposed by the atomic spin-orbit interaction. We realized the maximum magnetic anisotropy for a 3d transition metal atom by coordinating a single Co atom to the O site of an MgO(100) surface. Scanning tunneling spectroscopy reveals a record-high zero-field splitting of 58 millielectron volts as well as slow relaxation of the Co atom's magnetization. This striking behavior originates from the dominating axial ligand field at the O adsorption site, which leads to out-of-plane uniaxial anisotropy while preserving the gas-phase orbital moment of Co, as observed with x-ray magnetic circular dichroism.