A study of charge,energy and angular momentum transfer in the 56Fe + 197Au and 56Fe + 107, 109Ag reactions at 7.2 and 8.3 MeV/nucleon

Kinetic energy spectra, charge and angular distributions have been measured for thirty elements produced in the reactions of 401 and 460 MeV ⁵⁶Fe + ¹⁹⁷Au and in the reaction of 470 MeV ⁵⁶Fe + ^{107, 109}Ag. In addition, γ-ray multiplicities were measured at the 470 MeV bombarding energy for both targets at a limited number of angles. The charge distributions for the deep-inelastic component of these systems increase monotonically with atomic number in the measured angular range, whereas, those for the quasielastic component are skewed toward Z-values below the projectile. The angular distributions for the Fe-induced reactions show a smooth evolution from a side-peaked to forward-peaked distributions with increasing mass transfer. This side peak is more intense and more persistent for mass transfers from the projectile to the target. In the quasielastic region the γ-ray multiplicity is observed to increase almost linearly with decreasing Q-value whereas for large negative β-values it is essentially constant and independent of the exit channel mass asymmetry. Finally, angular distributions, angle-integrated charge distributions and γ-ray multiplicities have been compared with a diffusion model in which the dynamics of shape evolution, N/Z equilibration, angular momentum and energy exchange occur via one-body forces.     

Convection-diffusion of solutes in dynamic media

We investigate convective-diffusive transport of a solute through a medium with properties that can be externally modulated in space and time. In particular, we focus on the effect of a front—a sharp transition in the convective velocity (v) and diffusivity (D)—on the evolution of the solute concentration profile. Numerical results show that by suitably moving the front during the process an anti-dispersive effect may be realized, in which the solute accumulates in a thin region close to the moving boundary. Our computations take into account the realistic case of a front having a small but finite thickness, and we find that the width of the concentration profile scales as , where Pe is the Péclet number. This is in sharp contrast to the 1/Pe scaling observed for the ideal case of the singular front assumed in previous work. The effect of the thickness of the front and the magnitude of the drop inv andD, on the solute concentration profile has also been studied. These results are relevant in order to implement and optimize protocols that apply an externally controlled moving boundary for the purpose of separation. We also present experimental results characterizing solute transport across a stationary front, expected to display many features needed in a model for moving fronts. The concentration profile of electrophoretically mobile BSA-FITC within the boundary layer at a polyacrylamde gel-buffer interface were visualized by epifluorescence microscopy. Measured boundary layer thickness exceeded that predicted for even a finite interface, indicating that the length scale associated with real boundaries is relevant to the modeling problem.     

Molecular docking of cathepsin L inhibitors in the binding site of papain

The papain/CLIK-148 coordinate system was employed as a model to study the interactions of a nonpeptide thiocarbazate inhibitor of cathepsin L ( 1). This small molecule inhibitor, a thiol ester containing a diacyl hydrazine functionality and one stereogenic center, was most active as the S-enantiomer, with an IC 50 of 56 nM; the R-enantiomer ( 2) displayed only weak activity (33 microM). Correspondingly, molecular docking studies with Extra Precision Glide revealed a correlation between score and biological activity for the two thiocarbazate enantiomers when a structural water was preserved. The molecular interactions between 1 and papain were very similar to the interactions observed for CLIK-148 ( 3a and 3b) with papain, especially with regard to the hydrogen-bonding and lipophilic interactions of the ligands with conserved residues in the catalytic binding site. Subsequent docking of virtual compounds in the binding site led to the identification of a more potent inhibitor ( 5), with an IC 50 of 7.0 nM. These docking studies revealed that favorable energy scores and correspondingly favorable biological activities could be realized when the virtual compound design included occupation of the S2, S3, and S1' subsites by hydrophobic and aromatic functionalities of the ligand, and at least three hydrogen bonding contacts between the ligand and the conserved binding site residues of the protein.     

Decoupled bands in odd-mass mercury isotopes

The schemes of the low-lying high-spin states in mercury isotopes with A = 195, 197, and 199 have been studied by γ-ray spectroscopy following (α, xn) reactions on separated platinum targets. Two bands have been excited in each Hg nucleus, one with positive parity based on the isomeric i$\text{13}\text{2}$. state and one, probably with negative parity, starting at spin $\text{case21}\text{2}$. The positive-parity states are interpreted with the rotation-aligned coupling scheme as decoupled bands; this implies oblate deformation in these three Hg isotopes. The negative-parity states are discussed as a decoupled i$\text{13}\text{2}$ neutron state coupled to the 5^?, 7^?, 9^?,…states, recently discovered in doubly even mercury isotopes.