In(OH)BDC.0.75BDCH2 (BDC = Benzenedicarboxylate), a hybrid inorganic-organic vernier structure

The compound In(OH)BDC.0.75BDCH2 (BDC = benzenedicarboxylate), 1, has been synthesized and characterized by single-crystal X-ray diffraction. The structure comprises two distinct sublattices formed by a covalently linked In(OH)BDC lattice and ordered chains of hydrogen-bonded H2BDC molecules and can be described as a hybrid inorganic coordination polymer-organic vernier structure. Each InO6 octahedron of the octahedral chain has a length of 3.6 A along the chain axis, whereas each H2BDC molecule has a length of 9.6 A along the guest column axis. Therefore, a unit of eight InO6 octahedra of the octahedral chain is just in registry with three H2BDC molecules of the guest column giving a repeat unit of 28.76 A along the channel axis direction.     

Modeling and analyzing the performance of aviation security systems using baggage value performance measures

Aviation security is an important concern of national interest.Baggage screening security devices and operations at airportstations throughout the United States address this concern.Determining how and where to assign (deploy) such devices canbe quite challenging. Moreover, even after such systems arein place, it can be difficult to measure their effectiveness.Uncovered flight segment (UFS) and uncovered passenger segment(UPS) performance measures provide a useful framework for measuringthe effectiveness of a baggage screening security device deploymentto a given station. However, the optimization models associatedwith these measures do not consider baggage screening strategiesthat permit partial screening of flights. To allow for suchstrategies, as well as to identify baggage screening securitysystem models where the decision to screen each individual selecteebag is made individually (rather than collectively by flight),this paper introduces performance measures in which each selecteebag is assigned an individual value. In particular, the flightsegment baggage value (FSBV) assigns a value to each selecteebag based upon the proportion of the flight segment that thebag covers. The passenger segment baggage value (PSBV) assignsa value to each selectee bag based on the proportion of thepassenger segments that the bag covers. For each of these measures,an associated decision problem and integer programming modelare introduced. In addition, several results are presented detailingboth optimization techniques for the models associated witheach measure and the relationships between the baggage valuemeasures and other baggage screening security system measures.A real-world example using actual flight data from the officialairline guide is presented to illustrate an application of thesemodels and results.     

Extensions of the sequential stochastic assignment problem

The sequential stochastic assignment problem (SSAP) allocates N workers to N IID sequentially arriving tasks so as to maximize the expected total reward. This paper studies two extensions of the SSAP. The first one assumes that the values of any two consecutive tasks are dependent on each other while the exact number of tasks to arrive is unknown until after the final arrival. The second extension generalizes the first one by assuming that the number of workers is also random. Optimal assignment policies for both problems are derived and proven to have the same threshold structure as the optimal policy of the SSAP.     

Discovery of fluorescent cyanopyridine and deazalumazine dyes using small molecule macroarrays

[structure: see text] Small molecule macroarrays of cyanopyridines and deazalumazines were generated in high purities via spatially addressed synthesis on planar cellulose supports. Examination of the spectral properties of the heterocycles both on and off of the planar support revealed a set of promising new fluorescent dyes that exhibit high quantum yields, low pH dependence, and high sensitivity to solvent polarity.     

Evidence for an influence of local dipole excitations in thermal desorption

Ferroelectric crystalline copolymer films of vinylidene fluoride with trifluoroethylene (70%:30%) strongly interact with the dipoles of adsorbed and absorbed water molecules. This interaction can be probed with laser-assisted thermal desorption techniques. The UV light enhancement of water desorption is strongly light polarization dependent. The electronic structure of the ferroelectric copolymer films of vinylidene fluoride with trifluoroethylene films is locally altered with incident UV radiation suggesting metastable excited states that may involve dipole reorientation.     

Finding preferred subsets of Pareto optimal solutions

Multi-objective optimization algorithms can generate large sets of Pareto optimal (non-dominated) solutions. Identifying the best solutions across a very large number of Pareto optimal solutions can be a challenge. Therefore it is useful for the decision-maker to be able to obtain a small set of preferred Pareto optimal solutions. This paper analyzes a discrete optimization problem introduced to obtain optimal subsets of solutions from large sets of Pareto optimal solutions. This discrete optimization problem is proven to be NP-hard. Two exact algorithms and five heuristics are presented to address this problem. Five test problems are used to compare the performances of these algorithms and heuristics. The results suggest that preferred subset of Pareto optimal solutions can be efficiently obtained using the heuristics, while for smaller problems, exact algorithms can be applied.     

Demystifying the three dimensional structure of G protein-coupled receptors (GPCRs) with the aid of molecular modeling

We review our recent work on adenosine receptors, a family of GPCRs; focusing our attention on A3 adenosine receptor, we have demonstrated that the reciprocal integration of different theoretical and experimental disciplines can be very useful for the successful protein-based design of new, potent and selective receptor ligands.     

Ligand design by targeting a binding site water

Solvent reorganization is a major driving force of protein–ligand association, but the contribution of binding site waters to ligand affinity is poorly understood. We investigated how altered interactions with a water network can influence ligand binding to a receptor. A series of ligands of the A_2A adenosine receptor, which either interacted with or displaced an ordered binding site water, were studied experimentally and by molecular dynamics simulations. An analog of the endogenous ligand that was unable to hydrogen bond to the ordered water lost affinity and this activity cliff was captured by molecular dynamics simulations. Two compounds designed to displace the ordered water from the binding site were then synthesized and evaluated experimentally, leading to the discovery of an A_2A agonist with nanomolar activity. Calculation of the thermodynamic profiles resulting from introducing substituents that interacted with or displaced the ordered water showed that the gain of binding affinity was enthalpy driven. Detailed analysis of the energetics and binding site hydration networks revealed that the enthalpy change was governed by contributions that are commonly neglected in structure-based drug optimization. In particular, simulations suggested that displacement of water from a binding site to the bulk solvent can lead to large energy contributions. Our findings provide insights into the molecular driving forces of protein–ligand binding and strategies for rational drug design.

Solvent reorganization is a major driving force of protein–ligand association, but the contribution of binding site waters to ligand affinity is poorly understood.     

Novel microfabricated device for electrokinetically induced pressure flow and electrospray ionization mass spectrometry

A novel microchip device for electrospray ionization has been fabricated and interfaced to a time-of-flight mass spectrometer. Fluid is electrokinetically transported through the chip to a fine fused-silica capillary inserted directly into a channel at the edge of the device. Electrospray is established at the tip of the capillary, which assures a stable, efficient spray. The electric potential necessary for electrospray generation and the voltage drop for electroosmotic pumping are supplied through an electrically permeable glass membrane contacting the fluidic channel holding the capillary. The membrane is fabricated on the microchip using standard photolithographic and wet chemical etching techniques. Performance relative to other microchip electrospray sources has been evaluated and the device tested for potential use as a platform for on-line electrophoretic detection. Sensitivity was found to be approximately three orders of magnitude better than spraying from the flat edge of the chip. The effect of the capillary on electroosmotic flow was examined both experimentally and theoretically.