On the intrinsic conductivity of polysulphur-nitride

Polysulphur-nitride, (SN), is an unusually interesting polymer. Its solid phase and that of the parent molecular crystal have the same space group symmetry, with the same atoms and electrons per unit cell and very slight differences in bond lengths. Yet, they have completely different electronic properties. Accurate electronic structure calculations have been carried out for the polymer and molecular crystal phases at Hartree-Fock, Hartree and Local density Approximation levels. The results are qualitatively the same at these levels, and they are consistent with experimental observations. This shows that correlation does not play a deciding role. The results also re-emphasize a way to synthesize conducting polymers by polymerizing monomer molecules from their crystal phase. Simulations like in this work can be valuable to guide synthesis.     

Quasi-hermiticity and the Role of a Metric in Some Boson Hamiltonians

The strategy of endowing PT-symmetric quantum mechanics with a positive definite metric, by adopting a modified inner product, has recently been explored in a simple non-hermitian quadratic boson Hamiltonian. We reconsider this analysis with emphasis on the question of a unique metric linked to the identification of an irreducible set of observables. Our results emphasise the necessity to ensure such a unique metric in order to establish a viable quantum mechanical framework.     

On the Problem of the Amenability of the Gauge Group

Let G be one of the local gauge groups C(X, U(n)),C (X, U(n)), C(X, SU(n)) or C (X, SU(n)) where X is a compact Riemannian manifold. We observe that G has a nontrivial group topology, coarser than its natural topology, w.r.t. which it is amenable, viz. the relative weak topology of C(X, M(n)). This topology seems more useful than other known amenable topologies for G. We construct a simple fermionic model containing an action of G, continuous w.r.t. this amenable topology.     

Photodissociation of HCl and small (HCl)m complexes in and on large Ar n clusters

Photodissociation experiments were carried out at 193 nm for single HCl molecules which are adsorbed on the surface of large Ar n clusters and small (HCl)m complexes which are embedded in the interior of these clusters. For the surface case the size dependence is measured for the average sizes n=140-1000. No cage exit events are observed in agreement with the substitutional position of the molecule deeply buried in the outermost shell. This result is confirmed by a molecular dynamics simulation of the pickup process under realistic conditions concerning the experiment and the interaction potentials. The calculations of the dissociation process employ the surface hopping model. For the embedded case the average sizes covered are m=3 and 6 and n=8-248. The kinetic energy of the H atom fragments is measured exhibiting peaks at zero and around 2.0 eV which mark completely caged and unperturbed fragments, respectively. The ratio of theses peaks strongly depends on the cluster size and agrees well with theoretical predictions for one and two closed icosahedral shells, in which the nonadiabatic coupling of all states was accounted for.     

Synthesis of protein-nucleic acid conjugates by expressed protein ligation

The synthesis of covalent conjugates of proteins and polyamide nucleic acids (PNA) is accomplished by expressed protein ligation of intein-fusion proteins and a PNA-cysteine conjugate.     

Untersuchungen an Systemen aus Salzen und gemischten Lösungsmitteln. XXV [1]. Über den Einfluß von MgCl2 auf Aceton bzw. Aceton-Wasser-Gemische

Studies on systems of salts and mixed solvents. XXV. Effect of MgCl₂ on acetone and acetone-water mixtures In the sphere of the system Na⁺, K⁺, Mg⁺⁺/Cl^?//acetone-water being rich in acetone and especially with high intensity in the boundary system MgCl₂-acetone the formation of condensation products of acetone depending on temperature and time is observed. These reaction products, like e. g. 4-methyl-3-pentene-2-cene (mesityl oxide) and diacetone alcohol dye the solutions yellow to brown and influence the salt solubilities. MgCl₂ acts catalytically in form of Lewis acid on the aldol condensation of the acetone. As new solid phases MgCl₂ · 6 diacetone alcohol and MgCl₂ · 3 acetone are observed in the systems to be investigated.