Biomedical subjects
Publications and source records attributed to L Wiesenfeld.
Dynamical systems theory is used to construct a general phase-space version of transition state theory. Special multidimensional separatrices are found which act as impenetrable barriers in phase-space between reacting and nonreacting trajectories. The elusive momentum-dependent transition state between reactants and products is thereby characterized. A practical algorithm is presented and applied to a strongly coupled Hamiltonian.
We investigate the topological properties of the chaotic invariant set associated with the dynamics of scattering systems with three or more degrees of freedom. We show that the separation of one degree of freedom from the rest in the asymptotic regime, a common property in a large class of scattering models, defines a gate which is a dynamical object with phase space separating invariant manifolds. The manifolds form an invariant set causing singularities in the scattering process. The codimension one property of the manifolds ensures that the fractal structure of the invariant set can be studied by scattering functions defined over simple one-dimensional families of initial conditions as usually done in two-degree-of-freedom scattering problems. It is found that the fractal dimension of the invariant set is not due to the gates but to interior hyperbolic periodic orbits.
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The formula giving the parity-violating electroweak interaction contribution to the magnetic shielding tensor has been applied to enantiomers containing thallium. Using an extended Hückel relativistically parameterized method a chemical shift difference close to 1 mHz at 11.7 T is calculated in two couples of enantiomers. Such a difference is slightly lower than the extreme line width which may be actually reached in ultra-high resolution NMR.
Staphylococcus epidermidis, in contact with artificial surfaces, may produce a protective glue-like matrix or biofilm. The authors demonstrated that rifampin alone among 35 antibiotics penetrated the biofilm within a 24 hr exposure producing a major but incomplete killing. Antibiotics of the cell-wall active class (including vancomycin) were synergistic with rifampin, completing the bactericidal action. The addition of these antibiotics to a rifampin-vancomycin combination did not alter the synergy. Other antibiotics (including aminoglycosides) antagonized rifampin activity. This antagonism of rifampin was maintained when the antibiotics were added to the rifampin-vancomycin synergistic combination. These results may have implications for the choice of optimal therapeutic regimens in the management of implant-associated infection.