Two-stage integer programs with stochastic right-hand sides: a superadditive dual approach

We consider two-stage pure integer programs with discretely distributed stochastic right-hand sides. We present an equivalent superadditive dual formulation that uses the value functions in both stages. We give two algorithms for finding the value functions. To solve the reformulation after obtaining the value functions, we develop a global branch-and-bound approach and a level-set approach to find an optimal tender. We show that our method can solve randomly generated instances whose extensive forms are several orders of magnitude larger than the extensive forms of those instances found in the literature. This work is supported by National Science Foundation grants DMI-0217190 and DMI-0355433.     

Photodynamic therapy induces selective extravasation of macromolecules: Insights using intravital microscopy

Photodynamic therapy (PDT) with Visudyne^® acts by direct cellular phototoxicity and/or by an indirect vascular-mediated effect. Here, we demonstrate that the vessel integrity interruption by PDT can promote the extravasation of a macromolecular agent in normal tissue. To obtain extravasation in normal tissue PDT conditions were one order of magnitude more intensive than the ones in tissue containing neovessels reported in the literature.Fluorescein isothiocyanate dextran (FITC-D, 2000 kDa), a macromolecular agent, was intravenously injected 10 min before (LK0 group, n = 14) or 2 h (LK2 group, n = 16) after Visudyne^®-mediated PDT in nude mice bearing a dorsal skin fold chamber. Control animals had no PDT (CTRL group, n = 8). The extravasation of FITC-D from blood vessels in striated muscle tissue was observed in both groups in real-time for up to 2500 s after injection. We also monitored PDT-induced leukocyte rolling in vivo and assessed, by histology, the corresponding inflammatory reaction score in the dorsal skin fold chambers.In all animals, at the applied PDT conditions, FITC-D extravasation was significantly enhanced in the PDT-treated areas as compared to the surrounding non-treated areas (p < 0.0001). There was no FITC-D leakage in the control animals. Animals from the LK0 group had significantly less FITC-D extravasation than those from the LK2 group (p = 0.0002). In the LK0 group FITC-D leakage correlated significantly with the inflammation (p < 0.001).At the selected conditions, Visudyne^®-mediated PDT promotes vascular leakage and FITC-D extravasation into the interstitial space of normal tissue. The intensity of vascular leakage depends on the time interval between PDT and FITC-D injection. This concept could be used to locally modulate the delivery of macromolecules in vivo.     

Identification and localization of organic coating degradation onset by impedance imaging

The aim of this work was to demonstrate the potential of a localized impedance measurement technique to identify and spatially localize the onset spots of polymeric coating degradation. The technique, which has not yet been applied in the field of organic coatings, utilizes atomic force microscopy (AFM) in contact mode. During the scan a single-frequency voltage perturbation signal is applied between the AFM tip and the coated metal substrate. A current response signal is registered. As a result an impedance map of the scanned region is created. The method was applied to investigation of acrylic coating degradation during exposure to UV radiation. Localized topography and impedance images revealed formation of micro-cracks in the coating layer, which gradually converted into through-the-coating defects with an increase in the irradiation time. Thus the method allowed early identification and localization of the sites of degradation onset, which was not possible using classical impedance measurement.     

Binuclear cyclopentadienylcobalt sulfur and phosphinidene complexes Cp2Co2E2 (E = S, PX): Comparison with their Iron carbonyl analogues

Density functional theory studies on a series of Cp₂Co₂E₂ derivatives (E = S and PX; X = H, Cl, OH, OMe, NH₂, NMe₂) predict global minimum butterfly structures with one Co-Co bond for the “body” of the butterfly and four Co-E bonds at the edges of the “wings” of the butterfly. Tetrahedrane structures with both Co-Co and E-E bonds are higher in energy for Cp₂Co₂S₂ and Cp₂Co₂(PH)₂ and are not found in the other systems. This differs from the corresponding Fe₂(CO)₆S₂ and Fe₂(CO)₆(PX)₂ derivatives where tetrahedrane structures are predicted to be the lowest energy structures for all cases except X = NR₂ and OH and such a tetrahedrane structure is found experimentally for Fe₂(CO)₆S₂. The butterfly structures for the Cp₂Co₂E₂ derivatives are of two types. For Cp₂Co₂(PX)₂ (X = H, OH, OMe, NH₂, NMe₂) the lowest energy structures are unsymmetrical butterflies Cp₂Co₂(P)(PX₂) with two X groups on one phosphorus atom and a lone pair on the other (naked) phosphorus atom. Related low-energy unsymmetrical butterfly Fe₂(CO)₆(P)(PX₂) structures, not observed in previous theoretical studies, are now found for the corresponding Fe₂(CO)₆(PX)₂ derivatives. Symmetrical butterfly singlet diradical structures with one X group on each phosphorus atom in relative cis or trans positions are also found for the Cp₂Co₂(PX)₂ derivatives and are the global minima for Cp₂Co₂(PCl)₂ as well as Cp₂Co₂S₂. In all cases the cis structures are of lower energy than the corresponding trans structures. Rhombus structures having neither Co-Co nor E-E bonds are also found for all of the Cp₂Co₂(PX)₂ derivatives but always at higher energies than the butterfly structures, ranging from 17 to 29 kcal/mol above the global minima.