Zweikernverbrückende Bis-N-acylthioharnstoffe–Liganden in Trimetallamacrocyclen und Chelatpolymeren

Binucleating Bis-N-acylthioureas – Ligands in Trimetallamacrocycles and Polynuclear Metal Chelates By symmetric linking of two bidentate N-acylthioureas two types of quadridentate bis-N-acylthioureas are available which act – after di-deprotonation – as bis-bidentate S, O ligands towards polyvalent metal ions. They can form oligomeric or polymeric, cyclic or chain chelates. With 1,1,1′,1′-tetraalkyl-3,3′-terephthaloyl-bis-thioureas (H₂L) we obtained oligomeric triangulotrimetalla macrocycles Ni₃L₃ and Cu₃L₃. They contain perimetric 27-membered rings, counting the internal oxygens, or 39-membered rings with the external sulfur atoms on the other hand, i. e. equal chalcogen atoms are in cis-positions within each chelate unit around the three metal ions. The trimetallamacrocyclic structure was proved by x-ray crystal and molecular structure analysis of Ni₃L₃ (alkyl = Et) or EPR of the corresponding Cu₃L₃. Diamin-linked bis-N-acylthioureas form insoluble 1:1 polymeric chelates.     

Natural polyene α-pyrones. Synthesis of (±)-citreoviral

The total synthesis of (±)-citreoviral(2) and also of $\text{iso}$-citreoviral(21), using two conceptually distinct approaches starting from methyl tiglate, are described.     

Spatial extension of quantum gravitational particles inR 4×K N

It is observed that the magnitude relationma ² l _P/c holds if the non-Euclidean incremental spatial volume associated with a fundamental particle of massm and radiusa is characteristically quantum gravitational in a Kaluza-Klein or superstringR ⁴×K ^N . HereR ⁴ is the four-dimensional Riemannian space-time of general relativity andK ^N is a small-scale, compact,N-dimensional space of characteristic quantum gravitational volumel _P ^N , withl _P (G/c ³)^1/2= 1.61×10^–33 cm denoting the Planck length. For the electron and electron neutrino (assumed to possess nonzero mass bounded empirically by <30 eV) the derived magnitude relationa(l _P/mc)^1/2 yields the estimatesa _e 2.5×10^–22 cm and 3.3×10^–20 cm, spatial extensions which may be detectable by way of fine-scale effects in SSC experiments.     

Distance functional and suprema of hyperspace topologies

Let CL(X) denote the nonempty closed subsets of a metrizable space X. We show that the Vietoris topology on CL(X) is the weakest topology on CL(X) such that A - d(x, A) is continuous for each x X and each admissible metric d. We also give a concrete presentation of the analogous weak topology for uniformly equivalent metrics, and are led to consider for an admissible metric d the weakest topology on CL(X) such that the gap functional (A, B) - {d(ta, b): a A, b B} is continuous on CL(X) × CL(X).Visiting the University of Minnesota.Visiting California State University, Los Angeles.     

The rotational band on the 9− isomer in180Ta

The new radon isotope¹⁹⁷Rn was produced in the reaction¹⁶⁹Tm(³⁵Cl, 7n)¹⁹⁷Rn using bombarding energies from 5.6 to 6.1 MeV/nucleon. Fusion products were separated in-flight from the primary beam using a gas-filled recoil separator. The alpha particle energy and half-life of¹⁹⁷Rn were measured to be (7260±7) keV and (65 _?14 ⁺²⁵ ) ms, respectively. Another new alpha line was assigned to an isomeric state in¹⁹⁷Rn for which an alpha particle energy of (7356±7) keV and a half-life of (19 _?4 ⁺⁸ ) ms were obtained.