Optimization viewpoint on Kalman smoothing, with applications to robust and sparse estimation

In this paper, we present the optimization formulation of the Kalman filtering and smoothing problems, and use this perspective to develop a variety of extensions and applications. We first formulate classic Kalman smoothing as a least squares problem, highlight special structure, and show that the classic filtering and smoothing algorithms are equivalent to a particular algorithm for solving this problem. Once this equivalence is established, we present extensions of Kalman smoothing to systems with nonlinear process and measurement models, systems with linear and nonlinear inequality constraints, systems with outliers in the measurements or sudden changes in the state, and systems where the sparsity of the state sequence must be accounted for. All extensions preserve the computational efficiency of the classic algorithms, and most of the extensions are illustrated with numerical examples, which are part of an open source Kalman smoothing Matlab/Octave package.Comment: 46 pages, 11 figure

Driving fiber diameters to the limit: nanoparticle-induced diameter reductions in electrospun photoactive composite nanofibers for organic photovoltaics

Electrospun photoactive nanofibers hold significant potential for enhanced photon absorption and charge transport in organic photovoltaics. However, electrospinning conjugated polymers with fiber diameters comparable to exciton diffusion lengths for efficient dissociation, is difficult. Previously, spinning sub-100 nm poly(3-hexylthiophene) (P3HT) fibers has required the auxiliary polymer, poly(ethylene oxide) (PEO), and large antisolvent additions. Therefore, its success differs considerably across donor polymers, due to variable antisolvent addition limits before precipitation. Herein, plasmonic nanoparticle infusion into P3HT nanofibers is used to modulate viscosity and deliver a novel and unrivaled strategy to achieve reduced fiber diameters. Following PEO removal, the fibers measure 55 nm in diameter, 30% lower than any previous report – providing the shortest exciton diffusion pathways to the heterojunction upon electron acceptor infiltration. The nanoparticle-containing nanofibers present a 58% enhancement over their pristine thin-film counterparts. ~17% is ascribed to plasmonic effects, demonstrated in thin-films, and the remainder to along-fiber polymer chain alignment, introduced by electrospinning. The anisotropy of light absorbed when polarized parallel versus perpendicular to the fibers increases from 0.88 to 0.62, suggesting the diameter reduction improves the alignment, resulting in greater electrospinning-induced enhancements. Controlled by the electrospinning behavior of PEO, our platform may be adapted to contemporary donor-acceptor systems

Role of Nox4 and Nox2 in Hyperoxia-Induced Reactive Oxygen Species Generation and Migration of Human Lung Endothelial Cells

Abstract In vascular endothelium, the major research focus has been on reactive oxygen species (ROS) derived from Nox2. The role of Nox4 in endothelial signal transduction, ROS production, and cytoskeletal reorganization is not well defined. In this study, we show that human pulmonary artery endothelial cells (HPAECs) and human lung microvascular endothelial cells (HLMVECs) express higher levels of Nox4 and p22phox compared to Nox1, Nox2, Nox3, or Nox5. Immunofluorescence microscopy and Western blot analysis revealed that Nox4 and p22phox, but not Nox2 or p47phox, are localized in nuclei of HPAECs. Further, knockdown of Nox4 with siRNA decreased Nox4 nuclear expression significantly. Exposure of HPAECs to hyperoxia (3-24h) enhanced mRNA and protein expression of Nox4, and Nox4 siRNA decreased hyperoxia-induced ROS production. Interestingly, Nox4 or Nox2 knockdown with siRNA upregulated the mRNA and protein expression of the other, suggesting activation of compensatory mechanisms. A similar upregulation of Nox4 mRNA was observed in Nox2 2/ko mice. Downregulation of Nox4, or pretreatment with N-acetylcysteine, attenuated hyperoxia-induced cell migration and capillary tube formation, suggesting that ROS generated by Nox4 regulate endothelial cell motility. These results indicate that Nox4 and Nox2 play a physiological role in hyperoxia-induced ROS production and migration of ECs. Antioxid. Redox Signal. 11, 747-764.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/78121/1/ars.2008.2203.pd

Non-steady state operation of polymer/TiO2 photovoltaic devices

We present data on the initial period of operation of Gilch-route NMH-PPV/TiO2 composite solar cells (CSCs) which show that during this period the CSCs operate in a non-steady state regime. The behavior is complex and may include a gradual rise of the open circuit voltage (V-oc) and of the short-circuit current density (J(sc)) with time, a passage through a maximum of either or both parameters, and even a sign reversal. The mechanisms most probably contributing to the transient processes are: i) diffusion driven redistribution of charges resulting in the build up of a quasi steady state charge density profile across the device; ii) photo-doping resulting in a relatively slow increase of the average charge carrier concentration and consequently of the conductivity of the device. The latter is responsible for a strong decrease in V-oc, and is evidenced by the significant increase in dark current after device illumination

Nanocomposite titanium dioxide/polymer photovoltaic cells: effects of TiO2 microstructure, time and illumination power.

Nanocomposite titanium dioxide/polymer photovoltaic cells have been fabricated using poly[2-(2-ethylhexyloxy)-5-methoxy-1,4-phenylenevinylene] (MEHPPV). Two different types of titanium dioxide were used, one synthesized using a sol-gel method, the other was a commercial paste. The crystal structure, porosity and absorption spectra of the titanium dioxide layers were measured, and the titanium dioxide synthesized using the sol-gel method had a much lower level of anatase. The photovoltaic properties of the ITO/TiO2/MEHPPV/Au cells, which were similar for both types of TiO2, were measured as a function of illumination power and compared with equivalent circuit models. A simple equivalent circuit model incorporating a diode, two resistances and a light induced current was inconsistent with the illumination - dependent data and was improved by adding an illumination dependent shunt resistance. A very long lived, photo-induced increase in dark current was observed, which could not be explained by a polymer degradation mechanism or an increase in temperature under illumination, but was more likely to be due to trapped charge

Mechanisms involved in acquisition of bla<inf>NDM</inf> genes by IncA/C<inf>2</inf> and IncFII<inf>Y</inf> plasmids

Copyright © 2016, American Society for Microbiology. All Rights Reserved. blaNDM genes confer carbapenem resistance and have been identified on transferable plasmids belonging to different incompatibility (Inc) groups. Here we present the complete sequences of four plasmids carrying a blaNDM gene, pKP1-NDM-1, pEC2-NDM-3, pECL3-NDM-1, and pEC4-NDM-6, from four clinical samples originating from four different patients. Different plasmids carry segments that align to different parts of the blaNDM region found on Acinetobacter plasmids. pKP1-NDM-1 and pEC2-NDM-3, from Klebsiella pneumoniae and Escherichia coli, respectively, were identified as type 1 IncA/C2 plasmids with almost identical backbones. Different regions carrying blaNDM are inserted in different locations in the antibiotic resistance island known as ARI-A, and ISCR1 may have been involved in the acquisition of blaNDM-3 by pEC2-NDM-3. pECL3-NDM-1 and pEC4-NDM-6, from Enterobacter cloacae and E. coli, respectively, have similar IncFIIY backbones, but different regions carrying blaNDM are found in different locations. Tn3-derived inverted-repeat transposable elements (TIME) appear to have been involved in the acquisition of blaNDM-6 by pEC4-NDM-6 and the rmtC 16S rRNA methylase gene by IncFIIY plasmids. Characterization of these plasmids further demonstrates that even very closely related plasmids may have acquired blaNDM genes by different mechanisms. These findings also illustrate the complex relationships between antimicrobial resistance genes, transposable elements, and plasmids and provide insights into the possible routes for transmission of blaNDM genes among species of the Enterobacteriaceae family

ABCD Neurocognitive Prediction Challenge 2019: Predicting individual residual fluid intelligence scores from cortical grey matter morphology

We predicted residual fluid intelligence scores from T1-weighted MRI data available as part of the ABCD NP Challenge 2019, using morphological similarity of grey-matter regions across the cortex. Individual structural covariance networks (SCN) were abstracted into graph-theory metrics averaged over nodes across the brain and in data-driven communities/modules. Metrics included degree, path length, clustering coefficient, centrality, rich club coefficient, and small-worldness. These features derived from the training set were used to build various regression models for predicting residual fluid intelligence scores, with performance evaluated both using cross-validation within the training set and using the held-out validation set. Our predictions on the test set were generated with a support vector regression model trained on the training set. We found minimal improvement over predicting a zero residual fluid intelligence score across the sample population, implying that structural covariance networks calculated from T1-weighted MR imaging data provide little information about residual fluid intelligence.Comment: 8 pages plus references, 3 figures, 2 tables. Submission to the ABCD Neurocognitive Prediction Challenge at MICCAI 201