Conference Seminar Timetabling

Participants at a conference held in 1985 were asked to select seminars that they wished to attend, before the schedule of seminars was constructed. The conference organizers were then faced with the problem of finding a timetable that would allow participants to attend the seminars they had chosen. This interesting combinatorial optimization problem is investigated here. A heuristic method, incorporating an annealing algorithm, is developed to help the organizers timetable similar conferences in the future.     

Structural assessment under uncertain parameters via interval analysis

An efficient health monitoring system for damage detection in civil engineering structures using on-line monitoring data is being developed to identify any possible damage in short time. The present work is based on the treatment of uncertainties, which is one of the basic common difficulties faced when modelling structures. A methodology, based on interval analysis (IA) theory [R.E. Moore, Interval Analysis, Prentice-Hall, Englewood Cliffs, NJ, 1966] applied to a numerical constraint satisfaction problem (CSP) [J.R. Casas, J.C. Matos, J.A. Figueiras, J. Vehí, O. García, P. Herrero, Bridge monitoring and assessment under uncertainty via interval analysis, in: Ninth International Conference On Structural Safety And Reliability—ICOSSAR2005, 2005. pp. 487–494], is implemented in the damage detection [J.R. Casas, J.C. Matos, J.A. Figueiras, J. Vehí, O. García, P. Herrero, Bridge monitoring and assessment under uncertainty via interval analysis, in: Ninth International Conference On Structural Safety And Reliability—ICOSSAR2005, 2005. pp. 487–494] and modelling system of a long-term monitoring project in order to achieve such an objective. An algorithm is being developed for using such methodology with the obtained data.     

Markov classes in certain finite quotients of artin’s braid group

This paper studies three finite quotients of the sequence of braid groups {B _n;n = 1,2,…}. Each has the property that Markov classes in {ie160-1} = ∐B _n pass to well-defined equivalence classes in the quotient. We are able to solve the Markov problem in two of the quotients, obtaining canonical representatives for Markov classes and giving a procedure for reducing an arbitrary representative to the canonical one. The results are interpreted geometrically, and related to link invariants of the associated links and the value of the Jones polynomial on the corresponding classes. This material is based upon work partially supported by the National Science Foundation under Grant No. DMS-8503758.     

Double-CO3(2-) centered [Co(II)5] wheel and modeling of its magnetic properties

A high-spin Co(II) cluster with a rare pentagonal molecular structure and formula [Co(5)(CO(3))(2)(bpp)(5)]ClO(4) (1; Hbpp is 2,6-bis(phenyliminomethyl)-4-methylphenolate) has been synthesized and characterized by single-crystal X-ray diffraction. This topology arises from fusing five [Co(2)(bpp)] moieties in a cyclic manner around two CO(3)(2-) central ligands, resulting in propeller-like configuration. The irregular coordination of the carbonate ions to the metal centers results in a combination of coordination numbers (CNs) of the Co(II) ions of five and six. The bulk magnetization of this complicated magnetically exchanged system has been modeled successfully by employing a matrix diagonalization technique. For this, the combination of S=3/2 ions (CN=5) with ions exhibiting strong spin-orbit coupling (CN=6) has been considered and a perturbative approach to handle the data in the whole studied range of temperatures (2-300 K) yielding parameters of g and D (for the five-coordinate Co(II) ions), of A, κ, λ, and Δ (for the metals with spin-orbit coupling) and of the exchange constants J. The agreement with results from DFT calculations, also presented here, is remarkable.     

Targeting of cancer cells using click-functionalized polymer capsules

Targeted delivery of drugs to specific cells allows a high therapeutic dose to be delivered to the target site with minimal harmful side effects. Combining targeting molecules with nanoengineered drug carriers, such as polymer capsules, micelles and polymersomes, has significant potential to improve the therapeutic delivery and index of a range of drugs. We present a general approach for functionalization of low-fouling, nanoengineered polymer capsules with antibodies using click chemistry. We demonstrate that antibody (Ab)-functionalized capsules specifically bind to colorectal cancer cells even when the target cells constitute less than 0.1% of the total cell population. This precise targeting offers promise for drug delivery applications.     

Comparison of A2E Cytotoxicity and Phototoxicity with all-trans-Retinal in Human Retinal Pigment Epithelial Cells†

All-trans-retinal is the precursor of A2E, a fluorophore within lipofuscin, which accumulates in human retinal pigment epithelial (hRPE) cells and contributes to age-related macular degeneration. Here we have compared the in vitro dark cytotoxicity and visible-light-mediated photoreactivity of all-trans-retinal and A2E in hRPE cells. All-trans-retinal caused distinct cytotoxicity in hRPE cells measured with cell metabolic activity (MTS) and lactate dehydrogenase release assays. Significant increases in intracellular oxidized glutathione (GSSG), extracellular GSH and GSSG levels and lipid hydroperoxide production were observed in cells incubated in the dark with 25 and 50 μm all-trans-retinal. Light modified all-trans-retinal’s harmful action and decreased extracellular glutathione and hydroperoxide levels. A2E (<25 μm ) did not affect cell metabolism or cytoplasmic membrane integrity in the dark or when irradiated. 25 μm A2E raised the intracellular GSSG level in hRPE cells to a much smaller extent than 25 μm all-trans-retinal. A2E did not induce glutathione efflux or hydroperoxide generation in the dark or after irradiation. These studies support our previous conclusions that although A2E may be harmful at high concentrations or when oxidized, its phototoxic properties are insignificant compared to those of all-trans-retinal. The endogenous production of A2E may serve as a protective mechanism to prevent damage to the retina by free all-trans-retinal.     

Copper(II) complexes of thioarylazo-pentanedione: Structures,magnetism, redox properties and correlation with DFT calculations

Copper(II) complexes of 3-((2-(alkylthio)phenylazo)-2,4-pentanedione, tridentate O, N, S donor ligands, are described in this work. Chloride bridged copper(II) polymers (1) and thiocyanato bridged copper(II) dimmers (2) are characterized by a single crystal X-ray diffraction study. The complexes show antiferromagnetic interactions, with J = −0.5 ± 0.1 cm⁻¹ (1a) and −25.8 ± 0.5 cm⁻¹ (2b), which implies stronger coupling in the –SCN-bridging compound. The spectra, redox and magnetism are explained by DFT studies.     

On-chip photoactivation of heterologously expressed rhodopsin allows kinetic analysis of G-protein signaling by surface plasmon resonance spectroscopy

Surface plasmon resonance spectroscopy allows the study of protein interaction dynamics in real-time. Application of this technique to G-protein coupled receptors, the largest family of receptors involved in signal transduction, has been complicated by their low level of expression and the critical dependence of their native conformation on the hydrophobic transmembrane lipid environment. Here, we investigate and compare three different strategies to immobilize rhodopsin, a prototypical G-protein coupled receptor on a sensor chip surface using antibodies and a lectin for receptor capturing. By further probing of different experimental conditions (pH, detergent type) we identified the optimal factors to maintain rhodopsin in a functional conformation and extended this approach to recombinant rhodopsin that was heterologously expressed in COS cells. Functional operation of rhodopsin on the sensor chip surface was proven by its activation and subsequent light-stimulated G-protein coupling. The influence of these experimental parameters on the association and dissociation kinetics of G-protein receptor coupling was determined. Thereby, we found that the kinetics of G_t interaction were not changed by the strategy of immobilization or the type of detergent. Regeneration of opsin directly on a chip allowed recycling of the immobilized native and recombinant receptor. Thus, the approach provides an experimental framework for choosing the most suitable conditions for the solubilization, immobilization, and for functional tests of rhodopsin on a biosensor surface.