Maleimide-activated aryl diazonium salts for electrode surface functionalization with biological and redox-active molecules

A versatile and simple method is introduced for formation of maleimide-functionalized surfaces using maleimide-activated aryl diazonium salts. We show for the first time electrodeposition of N-(4-diazophenyl)maleimide tetrafluoroborate on gold and carbon electrodes which was characterized via voltammetry, grazing angle FTIR, and ellipsometry. Electrodeposition conditions were used to control film thickness and yielded submonolayer-to-multilayer grafting. The resulting phenylmaleimide surfaces served as effective coupling agents for electrode functionalization with ferrocene and the redox-active protein cytochrome c. The utility of phenylmaleimide diazonium toward formation of a diazonium-activated conjugate, followed by direct electrodeposition of the diazonium-modified DNA onto the electrode surface, was also demonstrated. Effective electron transfer was obtained between immobilized molecules and the electrodes. This novel application of N-phenylmaleimide diazonium may facilitate the development of bioelectronic devices including biofuel cells, biosensors, and DNA and protein microarrays.     

Phase locking of lasers with intracavity polarization elements

New configurations for phase locking several laser beams with intracavity polarization elements are presented. With this configuration we demonstrated efficient phase lock of up to 24 ND:YAG laser beams with only two polarization beam displacers.     

Manifestations of the roton mode in dipolar Bose-Einstein condensates

We investigate the structure of trapped Bose-Einstein condensates (BECs) with long-range anisotropic dipolar interactions. We find that a small perturbation in the trapping potential can lead to dramatic changes in the condensate's density profile for sufficiently large dipolar interaction strengths and trap aspect ratios. By employing perturbation theory, we relate these oscillations to a previously identified "rotonlike" mode in dipolar BECs. The same physics is responsible for radial density oscillations in vortex states of dipolar BECs that have been predicted previously.     

Braess's paradox for the spectral gap in random graphs and delocalization of eigenvectors

We study how the spectral gap of the normalized Laplacian of a random graph changes when an edge is added to or removed from the graph. There are known examples of graphs where, perhaps counter‐intuitively, adding an edge can decrease the spectral gap, a phenomenon that is analogous to Braess's paradox in traffic networks. We show that this is often the case in random graphs in a strong sense. More precisely, we show that for typical instances of Erd?s‐Rényi random graphs G (n, p ) with constant edge density , the addition of a random edge will decrease the spectral gap with positive probability, strictly bounded away from zero. To do this, we prove a new delocalization result for eigenvectors of the Laplacian of G (n, p ), which might be of independent interest. © 2016 Wiley Periodicals, Inc. Random Struct. Alg., 50, 584–611, 2017     

Scheduling charter aircraft

We present a system that is used for scheduling charter aircraft. At the core of the system is an elastic set partitioning model that is embedded in a decision support system. The model assigns a set of flights that have to be performed to the available fleets of aircraft at minimal cost while satisfying all operational requirements. Flights that cannot be accommodated by the available fleets are sold off to other operators. The minimised costs include the cost of flying the aircraft, the cost of selling off flights, and penalties on violations of soft constraints. The system has been in daily operation for almost a year, and it provides high quality schedules and saves numerous hours to the schedulers.     

Further studies on heterocyclic arene imines. Preparation of 1a,9b-dihydroazirino[f][1,7]phenanthroline, 3b,4a-dihydroazirino-[2,3]phenaleno[1,9-g,h]quinoline and 1a,13b-dihydrodibenzo[1,2:6,7]phenazino[1,2-b]azirine

The syntheses of the K-imine derivatives of 1,7-phenanthroline, phenaleno[1,9-g,h]quinoline, and dibenzo[a,h]phenazine are described. The parent heterocyclic compounds 4, 9 and 14 were oxidized to the corresponding K-oxides, 5, 10 and 15 , which in turn were reacted with sodium azide in aqueous acetone. The resulting trans-azido alcohols were then cyclized with tributylphosphine to the title compounds 6, 11 and 16 .     

Kinetic bromine isotope effect: example from the microbial debromination of brominated phenols

The increasing use of kinetic isotope effects for environmental studies has motivated the development of new compound-specific isotope analysis techniques for emerging pollutants. Recently, high-precision bromine isotope analysis in individual brominated organic compounds was proposed, by the coupling of gas chromatography to a multi-collector inductively coupled plasma mass spectrometer using strontium as an external spike for instrumental bias correction. The present study, for the first time, demonstrates an application of this technique for determining bromine kinetic isotope effects during biological reaction, focusing on the reductive debromination of brominated phenols under anaerobic conditions. Results show bromine isotope enrichment factors (ε) of ?0.76?±?0.08, ?0.46?±?0.19, and ?0.20?±?0.06?‰ for the debromination of 4-bromophenol, 2,4-dibromophenol, and 2,4,6-tribromophenol, respectively. These values are rather low, yet still high enough to be obtained with satisfying certainty. This further implies that the analytical method may be also appropriate for future environmental applications.     

Modeling the Flow Pattern at the Fractured Granites in Porto Alegre, Brazil

The studied 25 by 30 km site of Porto Alegre Southern Brazil fractured granites, accounts for surface lineaments assumed to mimic its fractures. Observations address the lineaments spatial characteristics, significant deviations between stationary groundwater levels condensed at part of the domain while sparse at most of the area, and no pumping/injection rates. Fractured media feature, e.g., dead end pathways, lack of flow interconnections, and preferential infiltration paths. These characteristics are not in line with the implementation of continuum-based macroscopic balance equations. Subject to such data and the inherent features, the objective was to verify if with lumped parameter modeling (LPM) following a flow directed graph approach we can assess a groundwater flow pattern. We at first addressed the site lineaments layout for which the evaluation of the hydraulic heads revealed the existence of isolated lineament clusters, leading to flow or no-flow zones. Aiming at better spatial distribution of flow distributions and based on the site surface lineaments, we established a virtual fracture network (VFN) for which the domain was subdivided into representative elementary area (REA) cells. Each REA was chosen so that the ratio of all its lineament lengths over that of the cell area remained practically unchanged between two consecutive subdivisions. Within each REA, lineaments with similar geometrical characteristics were considered as segment groups. The VFN was established upon elongating segments that created intersection points with other stretched segments from cells at the circumference of a considered REA. The evaluated steady state hydraulic head was compared between two LPM solutions: (1) Referring to flow along the VFN branches between intersection points, and (2) Using a flux interconnected network (FIN) for which each REA was replaced by a pole communicating flow to other poles. Computation of the FIN approach was significantly less intense. Both of these approaches resolved with hydraulic head isolines consistently similar to those obtained by interpolation between the observed groundwater levels. One reported event of a Nitrate polluted well and its plausible contaminating source within the study domain, show that it is in line with the predicted resultant flow direction following the FIN map.