Restoring infrastructure systems: An integrated network design and scheduling (INDS) problem

We consider the problem of restoring services provided by infrastructure systems after an extreme event disrupts them. This research proposes a novel integrated network design and scheduling problem that models these restoration efforts. In this problem, work groups must be allocated to build nodes and arcs into a network in order to maximize the cumulative weighted flow in the network over a horizon. We develop a novel heuristic dispatching rule that selects the next set of tasks to be processed by the work groups. We further propose families of valid inequalities for an integer programming formulation of the problem, one of which specifically links the network design and scheduling decisions. Our methods are tested on realistic data sets representing the infrastructure systems of New Hanover County, North Carolina in the United States and lower Manhattan in New York City. These results indicate that our methods can be used in both real-time restoration activities and long-term scenario planning activities. Our models are also applied to explore the effects on the restoration activities of aligning them with the goals of an emergency manager and to benchmark existing restoration procedures.     

Discrete module categories and operations in K-theory

We study the categories of discrete modules for topological rings arising as the rings of operations in various kinds of topological K-theory. We prove that for these rings the discrete modules coincide with those modules which are locally finitely generated over the ground ring.     

Size dependence of exchange bias in Co/CoO nanostructures

In Co/CoO nanostructures, of dimensions l×3l, at small Co thickness (≈6,10 nm), a strong increase in the bias field and the associated coercive field are found as the nanostructure size is reduced from l=120 nm to l=30 nm. This property indicates that the characteristic length D(AF) within the antiferromagnet which governs exchange-bias effects is the nanostructure size. By contrast, at larger Co thickness (≈23 nm), the exchange-bias field does not depend on the nanostructure size, implying that D(AF) is smaller than the nanostructure size. The results are discussed in the framework of the Malozemoff model, taking into account that the coupling between CoO grains is weak. Exchange bias is dominated either by coupling within the antiferromagnetic layer (6- and 10-nm-thick Co samples) or by ferromagnetic-antiferromagnetic interfacial coupling (23-nm-thick Co sample).     

Investigation and Development of Quantum Dot-Encoded Microsphere Bioconjugates for DNA Detection by Flow Cytometry

The development of screening assays continues to be an active area of research in molecular diagnostics. Fluorescent microspheres conjugated to biomarkers (nucleic acids, proteins, lipids, carbohydrates) and analyzed on flow cytometer instruments offered a new approach for multiplexed detection platform in a suspension format. Quantum dots encoded into synthetic microspheres have the potentials to improve current screening bioassays and specifically suspension array technology. In this paper, commercialized quantum dot-encoded microsphere were evaluated and optimized as fluorescent probes to address some of the limitations of suspension array technologies. A comprehensive study was undertaken to adapt the bioconjugation procedure to the quantum dot-encoded microsphere structural and optical properties. Both the leaching-out of quantum dots and microspheres degradation under bioconjugation experimental conditions were minimized. A rapid, efficient and reproducible conjugation method was developed for the detection of single-stranded DNA with the commercialized quantum dot-encoded microsphere. Approximately ten thousand microspheres were conjugated to short amino-modified DNA sequences in one hour with high efficiency. The bioconjugated microspheres acting as fluorescent probes successfully detected a DNA target in suspension with high specificity. Quantum dot-encoded microsphere commercial products are limited which strongly prevents reproducible and comparative studies between laboratories. The method developed here contributes to the understanding of quantum dot-encoded microsphere reactivity, and to the optimization of adapted experimental procedure. This step is essential in the development of this new fluorescent probe technology for multiplex genotyping assay and molecular diagnostic applications.     

Radiation-induced cathodoluminescent signatures in calcite

At ambient temperatures, a permanent change due to neutron irradiation has been identified in the luminescent properties of the common mineral calcite. Calcite is one of many ubiquitous minerals that are known to exhibit luminescence under electron bombardment, a process known as cathodoluminescence (CL). The UV–Visible spectra of individual calcite grains were measured with CL spectroscopy before and after neutron irradiation. Exposure to neutrons causes additional crystal lattice defects (beyond those naturally-occurring) that leave a permanent, readily-measurable CL signature in the 515 nm region of the spectrum. Dose response results following irradiation have been measured and a spectroscopic signature is described that increases proportionately to neutron dose. The CL measurements are complicated by a dependence on the orientation relative to direction of excitation. When taken into account, the total dose to the crystal can be estimated, and possibly even the direction of the neutron source can be determined. This signature could potentially be developed into a nuclear forensics tool to help identify locations where special nuclear materials have been stored.     

3D sensitivity encoded ellipsoidal MR spectroscopic imaging of gliomas at 3T

Purpose

The goal of this study was to implement time efficient data acquisition and reconstruction methods for 3D magnetic resonance spectroscopic imaging (MRSI) of gliomas at a field strength of 3T using parallel imaging techniques.

Methods

The point spread functions, signal to noise ratio (SNR), spatial resolution, metabolite intensity distributions and Cho:NAA ratio of 3D ellipsoidal, 3D sensitivity encoding (SENSE) and 3D combined ellipsoidal and SENSE (e-SENSE) k-space sampling schemes were compared with conventional k-space data acquisition methods.

Results

The 3D SENSE and e-SENSE methods resulted in similar spectral patterns as the conventional MRSI methods. The Cho:NAA ratios were highly correlated (P<.05 for SENSE and P<.001 for e-SENSE) with the ellipsoidal method and all methods exhibited significantly different spectral patterns in tumor regions compared to normal appearing white matter. The geometry factors ranged between 1.2 and 1.3 for both the SENSE and e-SENSE spectra. When corrected for these factors and for differences in data acquisition times, the empirical SNRs were similar to values expected based upon theoretical grounds. The effective spatial resolution of the SENSE spectra was estimated to be same as the corresponding fully sampled k-space data, while the spectra acquired with ellipsoidal and e-SENSE k-space samplings were estimated to have a 2.36–2.47-fold loss in spatial resolution due to the differences in their point spread functions.

Conclusion

The 3D SENSE method retained the same spatial resolution as full k-space sampling but with a 4-fold reduction in scan time and an acquisition time of 9.28 min. The 3D e-SENSE method had a similar spatial resolution as the corresponding ellipsoidal sampling with a scan time of 4:36 min. Both parallel imaging methods provided clinically interpretable spectra with volumetric coverage and adequate SNR for evaluating Cho, Cr and NAA.     

Synthesis of pyrrolidin-3-ones from dihydropyran precursors via spiro-N,O-acetals

2,2-Disubstituted pyrrolidin-3-ones are prepared in three steps from simple dihydropyran derivatives; the key spiro-N,O-acetal intermediate is a useful N-sulfonylketoiminium ion precursor. This route represents a formal synthesis of the indolizidine alkaloid core, with potential application to pyrrolizidines and quinolizidines.     

Analysis of fluorotelomer alcohols in soils: Optimization of extraction and chromatography

This article describes the development of an analytical method for the determination of fluorotelomer alcohols (FTOHs) in soil. The sensitive and selective determination of the telomer alcohols was performed by extraction with methyl tert-butyl ether (MTBE) and analysis of the extract using gas chromatography with detection and quantification by mass spectrometry operated in the positive chemical ionization mode. The protonated molecular ion, [M+H]⁺ and a fragment ion (loss of HF + H₂O) m/z 38 less than the molecular ion were monitored to identify tentatively FTOHs in MTBE extracts of contaminated soils. The FTOHs were confirmed by treatment of the extract with a silylation reagent and observing the disappearance of the FTOH response and the appearance of peaks attributable to the [M+H]⁺ ions of the trimethylsilyl derivatives. Mass-labeled FTOHs were used as recovery and matrix internal standards. Recovery experiments on soils shown to be free of endogenous FTOHs at instrument detection limits (IDL) of 16 fg/μL for 6:2 FTOH, 10 fg/μL for 8:2 FTOH and 14 fg/μL for 10:2 FTOH yielded a limit of quantitation (LOQ) of 190, 100, and 160 fg/μL for 6:2 FTOH, 8:2 FTOH, and 10:2 FTOH, respectively when 3 g samples of soil were extracted with 1 mL MTBE. The levels of the 6:2 FTOH, 8:2 FTOH, and 10:2 FTOH in five soils contaminated with FTOHs by exposure to the laboratory atmosphere during air drying were determined. In these air-dried soils, concentrations of FTOHs ranged from non-detectable to 3600 fg/μL (0.6 ng/g) of the 6:2 FTOH in the extract of a commercial topsoil. This method was used to determine even and odd numbered FTOHs from 6:2 through 14:2 in soils from fields that had received applications of sewage sludge. Concentrations of FTOHs in these sludge-applied soils ranged as high as 820 ng/g of dry soil for the 10:2 FTOH.     

Fluorocarbon-hydrocarbon incompatibility in micellar polymerizations

A new approach to micellar polymerization is described. It is well known that hydrocarbons and fluorocarbons exhibit local phase segregation (demixing) owing to mutual antipathy; here this effect is employed in monomer swollen micelles with appropriate combinations of hydrocarbon and fluorocarbon monomers and surfactants. A matrix of these hydro- and fluorocarbon components has been investigated to delineate the effects of H–F antipathy on the outcomes of polymerization reactions to generate nanolatices of different size (and possibly morphology). Phase diagrams, ¹H NMR and small-angle neutron (SANS) data have been generated to characterize the systems, indicating new routes to influence nanolatex formation.     

Prospective elementary teachers use of representation to reason algebraically

We used a teaching experiment to evaluate the preparation of preservice teachers to teach early algebra concepts in the elementary school with the goal of improving their ability to generalize and justify algebraic rules when using pattern-finding tasks. Nearly all of the elementary preservice teachers generalized explicit rules using symbolic notation but had trouble with justifications early in the experiment. The use of isomorphic tasks promoted their ability to justify their generalizations and to understand the relationship of the coefficient and y-intercept to the models constructed with pattern blocks. Based on critical events in the teaching experiment, we developed a scale to map changes in preservice teachers’ understanding. Features of the tasks emerged that contributed to this understanding.