Generalized Descent Methods for Asymmetric Systems of Equations and Variational Inequalities

We consider generalizations of the steepest descent algorithm for solving asymmetric systems of equations. We first show that if the system is linear and is defined by a matrix M, then the method converges if M2 is positive definite. We also establish easy to verify conditions on the matrix M that ensure that M is positive definite, and develop a scaling procedure that extends the class of matrices that satisfy the convergence conditions. In addition, we establish a local convergence result for nonlinear systems defined by uniformly monotone maps, and discuss a class of general descent methods. Finally, we show that a variant of the Frank-Wolfe method will solve a certain class of variational inequality problems. All of the methods that we consider reduce to standard nonlinear programming algorithms for equivalent optimization problems when the Jacobian of the underlying problem map is symmetric. We interpret the convergence conditions for the generalized steepest descent algorithms as restricting the degree of asymmetry of the problem map

The Effect of Simazine, Kinetin, and Rhizobium Phaesoli on Legume Nodulation and Morphogenesis in Phaseolus Vularis L., cv. "Red Kidney"

Author Institution: Department of Botany, Howard University, Washington, D.C.The growth responses of Phaseolus vulgaris L., cv. "Red Kidney" plants to simazine at 5 x 10~5M and 5 x 10^6M, kinetin at 9 x 10~7M and 9 x 10~8M, and the presence or absence of Rhizobium phaseoli ATCC14482, in factorial combination, were measured. The plants were analyzed with respect to the lengths of the primary-through-quaternary leaves, stem height, fresh and dry weights, number of flowers, and number and size of nodules. An analysis of variance showed that simazine significantly depressed all parameters at both concentrations. Kinetin did not affect the lengths of the primary-through-tertiary leaves, but depressed the quaternary, and also decreased dry weights at the higher concentration. Kinetin had no effect on stem height; it decreased flowering, but enhanced modulation. The presence of Rhizobium had a significant effect only on flowering and nodulation, increasing both

The elimination of surface cross-hatch from relaxed, limited-area Si1 – xGex buffer layers

The influence of lateral dimensions on the relaxation and surface topography of linearly graded Si1 – xGex buffer layers has been investigated. A dramatic change in the relaxation mechanism has been observed for depositions on Si mesa pillars of lateral dimensions 10 µm and below. Misfit dislocations are able to extend unhindered and terminate at the edges of the growth zone, yielding a surface free of cross-hatch. For lateral dimensions in excess of 10 µm orthogonal misfit interactions occur and relaxation is dominated by the modified Frank–Read (MFR) mechanism. The stress fields associated with the MFR dislocation pile-ups result in a pronounced cross-hatch topography

Controlling the Location and Spatial Extent of Nanobubbles Using Hydrophobically Nanopatterned Surfaces

The presence of nanobubbles—as imaged with tapping-mode atomic force microscopy— is controlled using nanopatterned surfaces possessing repeating patterns of polystyrene (hydrophobic domains) and polymethyl-methacrylate (hydrophilic domains). For nanobubbles to be present, we find that, in addition to controlling the degree of surface hydrophobicity, it is important for the spatial dimensions of the hydrophobic domains on the nanopatterned surface to be commensurate with the equilibrium topology of the nanobubbles.NSF-NIRT (Nanoscale Interdisciplinary Research Team on Nanoscale Wetting

Anr and Its Activation by PlcH Activity in Pseudomonas aeruginosa Host Colonization and Virulence

Pseudomonas aeruginosa hemolytic phospholipase C (PlcH) degrades phosphatidylcholine (PC), an abundant lipid in cell membranes and lung surfactant. A ΔplcHR mutant, known to be defective in virulence in animal models, was less able to colonize epithelial cell monolayers and was defective in biofilm formation on plastic when grown in lung surfactant. Microarray analyses found that strains defective in PlcH production had lower levels of Anr-regulated transcripts than the wild type. PC degradation stimulated the Anr regulon in an Anr-dependent manner under conditions where Anr activity was submaximal because of the presence of oxygen. Two PC catabolites, choline and glycine betaine (GB), were sufficient to stimulate Anr activity, and their catabolism was required for Anr activation. The addition of choline or GB to glucose-containing medium did not alter Anr protein levels, growth rates, or respiratory activity, and Anr activation could not be attributed to the osmoprotectant functions of GB. The Δanr mutant was defective in virulence in a mouse pneumonia model. Several lines of evidence indicate that Anr is important for the colonization of biotic and abiotic surfaces in both P. aeruginosa PAO1 and PA14 and that increases in Anr activity resulted in enhanced biofilm formation. Our data suggest that PlcH activity promotes Anr activity in oxic environments and that Anr activity contributes to virulence, even in the acute infection phase, where low oxygen tensions are not expected. This finding highlights the relationships among in vivo bacterial metabolism, the activity of the oxygen-sensitive regulator Anr, and virulence

Prevalence of suicidal behaviour following traumatic brain injury: Longitudinal follow-up data from the NIDRR Traumatic Brain Injury Model Systems

Objective: This study utilized the Traumatic Brain Injury Model Systems (TBIMS) National Database to examine the prevalence of depression and suicidal behaviour in a large cohort of patients who sustained moderate-to-severe TBI. Method: Participants presented to a TBIMS acute care hospital within 72 hours of injury and received acute care and comprehensive rehabilitation in a TBIMS designated brain injury inpatient rehabilitation programme. Depression and suicidal ideation were measured with the Patient Health Questionnaire (PHQ-9). Self-reported suicide attempts during the past year were recorded at each follow-up examination, at 1, 2, 3, 10, 15 and 20 years post-injury. Results: Throughout the 20 years of follow-up, rates of depression ranged from 24.8–28.1%, suicidal ideation ranged from 7.0–10.1% and suicide attempts (past year) ranged from 0.8–1.7%. Participants who endorsed depression and/or suicidal behaviour at year 1 demonstrated consistently elevated rates of depression and suicidal behaviour 5 years after TBI. Conclusion: Compared to the general population, individuals with TBI are at greater risk for depression and suicidal behaviour many years after TBI. The significant psychiatric symptoms evidenced by individuals with TBI highlight the need for routine screening and mental health treatment in this population

Modelling the population size and dynamics of the British grey seal

Funding: part-funded by the UK Natural Environment Research Council to SMRU (Grant no. SMRU1001).1. Grey seals (Halichoerus grypus) were the first mammals to be protected by an Act of Parliament in the UK and are currently protected under UK, Scottish, and EU conservation legislation. Reporting requirements under each of these statutes requires accurate and timely population estimates. Monitoring is principally conducted by aerial surveys of the breeding colonies; these are used to produce estimates of annual pup production. Translating these data to estimates of adult population size requires information about demographic parameters such as fecundity and sex ratio. 2. An age‐structured population dynamics model is presented, which includes density dependence in pup survival, with separate carrying capacities in each of the four breeding regions considered (North Sea, Inner Hebrides, Outer Hebrides, and Orkney). This model is embedded within a Bayesian state–space modelling framework, allowing the population model to be linked to available data and the use of informative prior distributions on demographic parameters. A computer‐intensive fitting algorithm is presented based on particle filtering methods. 3. The model is fitted to region‐level pup production estimates from 1984 to 2010 and an independent estimate of adult population size, derived from aerial surveys of hauled‐out seals in 2008. The fitted model is used to estimate total population size from 1984 to 2010. 4. The population in the North Sea region has increased at a near‐constant rate; growth in the other three regions began to slow in the mid‐1990s and these populations appear to have reached carrying capacity. The total population size of seals aged 1 year or older in 2010 was estimated to be 116 100 (95% CI 98 400–138 600), an increase of <1% on the previous year. 5. The modelling and fitting methods are widely applicable to other wildlife populations where diverse sources of information are available and inference is required for the underlying population dynamics.PostprintPeer reviewe

The Clean Power Plan: Issues to Watch

Although the Clean Air Act is an imperfect tool for addressing the nation’s greenhouse gas emissions, it is the only available federal mechanism for directly addressing power plant carbon emissions. The Obama Administration’s Clean Power Plan, published in final form in August 2015, tackles the challenge. This paper from the Center for Progressive Reform (CPR) compiles 13 separately authored essays from 11 CPR Member Scholars, each addressing a different topic related to the Clean Power Plan, and each representing the expertise and views of its individual author(s). Published in July 2015, just before the release of the final rule, the essays tee up key questions about the rule’s legality, implications for the energy sector, and a series of discrete implementation questions, including the role of cap-and-trade (and offsets), the nature and distribution of state targets, and implications for environmental justice

Insights into the influence of solvent polarity on the crystallization of poly(ethylene oxide) spin-coated thin films via in situ grazing incidence wide-angle X-ray scattering

Controlling polymer thin-film morphology and crystallinity is crucial for a wide range of applications, particularly in thin-film organic electronic devices. In this work, the crystallization behavior of a model polymer, poly(ethylene oxide) (PEO), during spin-coating is studied. PEO films were spun-cast from solvents possessing different polarities (chloroform, THF, and methanol) and probed via in situ grazing incidence wide-angle X-ray scattering. The crystallization behavior was found to follow the solvent polarity order (where chloroform chloroform > methanol). When spun-cast from nonpolar chloroform, crystallization largely followed Avrami kinetics, resulting in the formation of morphologies comprising large spherulites. PEO solutions cast from more polar solvents (THF and methanol) do not form well-defined highly crystalline morphologies and are largely amorphous with the presence of small crystalline regions. The difference in morphological development of PEO spun-cast from polar solvents is attributed to clustering phenomena that inhibit polymer crystallization. This work highlights the importance of considering individual components of polymer solubility, rather than simple total solubility, when designing processing routes for the generation of morphologies with optimum crystallinities or morphologies

The Clean Power Plan: Issues to Watch

Although the Clean Air Act is an imperfect tool for addressing the nation’s greenhouse gas emissions, it is the only available federal mechanism for directly addressing power plant carbon emissions. The Obama Administration’s Clean Power Plan, published in final form in August 2015, tackles the challenge. This paper from the Center for Progressive Reform (CPR) compiles 13 separately authored essays from 11 CPR Member Scholars, each addressing a different topic related to the Clean Power Plan, and each representing the expertise and views of its individual author(s). Published in July 2015, just before the release of the final rule, the essays tee up key questions about the rule’s legality, implications for the energy sector, and a series of discrete implementation questions, including the role of cap-and-trade (and offsets), the nature and distribution of state targets, and implications for environmental justice