Het laatste woord? : de ontwikkeling van de discussie over het Schriftgezag

Masterthesis Gemeentepredikan

Specific Heat, Susceptibility and High-Field Magnetisation Experiments on Heavy Fermion UPt3 Alloyed with Pd

Specific heat, susceptibility and high-field magnetisation experiments have been performed on a number of pseudobinary U(Pt1-xPdx)3 compounds with x ≤ 0.30. For low Pd concentrations (x ≤ 0.10) the spin-fluctuation contribution to the specific heat is enhanced with respect to pure UPt3. For x ≥ 0.15 the spin-fluctuation phenomena are lost. On alloying, the anomalies present for UPt3 in the susceptibility at 17 K and in the high-field magnetisation at 21 T (at 4.2 K), shift towards lower temperatures and fields, respectively, and have not been observed in a compound with x = 0.15. Superconductivity has not been found down to 40 mK in a U(Pt0.995Pd0.005)3 sample

Possible Heavy-Fermion Behaviour of New U(Cu, Al)5 Compounds

We have synthesized several new UCuxAl5 - x compounds in the composition range between x = 2.9 and x = 3.5, which were found to form in crystal structures related to the CaCu5 structure. Specific-heat measurements reveal a considerable enhancement of the low-temperature specific-heat coefficient γ for all U(Cu, Al)5 compounds investigated, with a maximum value of 450 mJ/molK2 at 1.2 K for UCu2.9Al2.1. © 1995.Acknowledgement: Work was supported by the "Sticht-ing voor Fundamenteel Onderzoek der Materie" (FOM)

Possible heavy-fermion behaviour of new U(Cu, Al)5 compounds

We have synthesized several new UCuxAl5 - x compounds in the composition range between x = 2.9 and x = 3.5, which were found to form in crystal structures related to the CaCu5 structure. Specific-heat measurements reveal a considerable enhancement of the low-temperature specific-heat coefficient γ for all U(Cu, Al)5 compounds investigated, with a maximum value of 450 mJ/molK2 at 1.2 K for UCu2.9Al2.1. © 1995.Acknowledgement: Work was supported by the "Sticht-ing voor Fundamenteel Onderzoek der Materie" (FOM)

The superconducting ferromagnet UCoGe

The correlated metal UCoGe is a weak itinerant ferromagnet with a Curie temperature T_C = 3 K and a superconductor with a transition temperature T_s = 0.6 K. We review its basic thermal, magnetic - on the macro and microscopic scale - and transport properties, as well as the response to high pressure. The data unambiguously show that superconductivity and ferromagnetism coexist below T_s = 0.6 K and are carried by the same 5f electrons. We present evidence that UCoGe is a p-wave superconductor and argue that superconductivity is mediated by critical ferromagnetic spin fluctuations.Comment: 19 pages; review paper; accepted for publication in the Journal of Low Temperature Physics (Special issue: Quantum Phase Transitions 2010

Putative role of the adenosine A3 receptor in the antiproliferative action of N6-(2-isopentenyl)adenosine

We tested a panel of naturally occurring nucleosides for their affinity towards adenosine receptors. Both N6-(2-isopentenyl)adenosine (IPA) and racemic zeatin riboside were shown to be selective human adenosine A3 receptor (hA3R) ligands with affinities in the high nanomolar range (Ki values of 159 and 649 nM, respectively). These values were comparable to the observed Ki value of adenosine on hA3R, which was 847 nM in the same radioligand binding assay. IPA also bound with micromolar affinity to the rat A3R. In a functional assay in Chinese hamster ovary cells transfected with hA3R, IPA and zeatin riboside inhibited forskolin-induced cAMP formation at micromolar potencies. The effect of IPA could be blocked by the A3R antagonist VUF5574. Both IPA and reference A3R agonist 2-chloro-N6-(3-iodobenzyl)adenosine-5′-N-methylcarboxamide (Cl-IB-MECA) have known antitumor effects. We demonstrated strong and highly similar antiproliferative effects of IPA and Cl-IB-MECA on human and rat tumor cell lines LNCaP and N1S1. Importantly, the antiproliferative effect of low concentrations of IPA on LNCaP cells could be fully blocked by the selective A3R antagonist MRS1523. At higher concentrations, IPA appeared to inhibit cell growth by an A3R-independent mechanism, as was previously reported for other A3R agonists. We used HPLC to investigate the presence of endogenous IPA in rat muscle tissue, but we could not detect the compound. In conclusion, the antiproliferative effects of the naturally occurring nucleoside IPA are at least in part mediated by the A3R

Functional selectivity of adenosine receptor ligands

Adenosine receptors are plasma membrane proteins that transduce an extracellular signal into the interior of the cell. Basically every mammalian cell expresses at least one of the four adenosine receptor subtypes. Recent insight in signal transduction cascades teaches us that the current classification of receptor ligands into agonists, antagonists, and inverse agonists relies very much on the experimental setup that was used. Upon activation of the receptors by the ubiquitous endogenous ligand adenosine they engage classical G protein-mediated pathways, resulting in production of second messengers and activation of kinases. Besides this well-described G protein-mediated signaling pathway, adenosine receptors activate scaffold proteins such as β-arrestins. Using innovative and sensitive experimental tools, it has been possible to detect ligands that preferentially stimulate the β-arrestin pathway over the G protein-mediated signal transduction route, or vice versa. This phenomenon is referred to as functional selectivity or biased signaling and implies that an antagonist for one pathway may be a full agonist for the other signaling route. Functional selectivity makes it necessary to redefine the functional properties of currently used adenosine receptor ligands and opens possibilities for new and more selective ligands. This review focuses on the current knowledge of functionally selective adenosine receptor ligands and on G protein-independent signaling of adenosine receptors through scaffold proteins