Curve fitting of time-series Landsat imagery for characterizing a mountain pine beetle infestation

In this technical note we present a new technique using mixed linear models for characterizing a mountain pine beetle (Dendroctonus ponderosae Hopkins) infestation from multiyear satellite imagery. The main benefit of our approach is an ability to determine the statistical significance of each annual spectral change. Knowledge of the annual spectral change characteristics can then be used to statistically determine if a disturbance event has occurred, the timing of a given disturbance event, as well as to provide information for clustering fitted multitemporal reflectance curves (i.e. spectral trajectories) with a common shape. The spatial clustering of spectral trajectories provides insights into the nature of the disturbance and recovery imposed by infestation over a 14-year period.     

An algebraic approach to decoupling in linear multivariable systems

This paper examines the problem of decoupling designs for linear multivariable systems. Both partial and diagonal decoupling designs are considered. The development is based on an algebraic approach and the use of coprime factorizations, which provide a mechanism to account for key system properties including internal stability and decoupling invariants. The results obtained include necessary and sufficient conditions for decoupling and a parametrization of all decoupling controllers.     

Frequency domain design trade-offs for linear periodic feedback systems*

The purpose of this paper is to analyse inherent design limitations associated with systems that are linear and periodically time-varying. The contributions of the paper are (i) to relate frequency domain raising methods from signal processing literature to time-domain lifting used in control literature, and (ii) to develop extensions of the Poisson sensitivity and complementary sensitivity integral constraints. In particular, it is shown that there is generally an additional cost associated with having a time invariant target closed loop for a periodic open loop plant. It is also shown that design limitations due to unstable poles and/or non-minimum phase zeros of a discrete linear time-invariant plant remain even if a periodic time-varying controller is used. As a consequence, the utility of periodic control in circumventing design limitations is questioned.     

The diversity of retrotransposons in the yeast Cryptococcus neoformans.

We have undertaken an analysis of the retrotransposons in the medically important basidiomycetous fungus Cryptococcus neoformans. Using the data generated by a C. neoformans genome sequencing project at the Stanford Genome Technology Center, 15 distinct families of LTR retrotransposons and several families of non-LTR retrotransposons were identified. Members of at least seven families have transposed recently and are probably still active. For several families, only partial elements could be identified and these are quite diverse in sequence, suggesting that they are ancient components of the C. neoformans genome. Most C. neoformans elements are not closely related to previously identified fungal retrotransposons, suggesting that the diversity of fungal retrotransposons has been only sparsely sampled to date. C. neoformans has fewer distinct retrotransposon families than Candida albicans (37 or more), in particular fewer families represented solely by ancient and inactive elements, but it has considerably more families than either Saccharomyces cerevisiae (five) or Schizosaccharomyces pombe (two). The findings suggest that elimination of retrotransposons is faster in C. neoformans than in C. albicans, but perhaps not as rapid as in S. cerevisiae or Sz. pombe. The identification of the retrotransposons of C. neoformans should assist in the molecular characterization of this important pathogen, and also further our understanding of the role played by retroelements in genome evolution.     

Orchestration of neutrophil movement by intestinal epithelial cells in response to Salmonella typhimurium can be uncoupled from bacterial internalization

Intestinal epithelial cells respond to Salmonella typhimurium by internalizing this pathogen and secreting, in a polarized manner, an array of chemokines which direct polymorphonuclear leukocyte (PMN) movement. Notably, interleukin-8 (IL-8) is secreted basolaterally and directs PMN through the lamina propria, whereas pathogen-elicited epithelial chemoattractant (PEEC) is secreted apically and directs PMN migration across the epithelial monolayer to the intestinal lumen. While most studies of S. typhimurium pathogenicity have focused on the mechanism by which this bacterium invades its host, the enteritis characteristically associated with salmonellosis appears to be more directly attributable to the PMN movement that occurs in response to this pathogen. Therefore, we sought to better understand the relationship between S. typhimurium invasion and epithelial promotion of PMN movement. First, we investigated whether S. typhimurium becoming intracellular was necessary or sufficient to induce epithelial promotion of PMN movement. Blocking S. typhimurium invasion by preventing, with cytochalasin D, the epithelial cytoskeletal rearrangements which mediate internalization did not reduce the epithelial promotion of PMN movement. Conversely, bacterial attainment of an intracellular position was not sufficient to induce model epithelia to direct PMN transmigration, since neither basolateral invasion by S. typhimurium nor apical internalization of an invasion-deficient mutant (achieved by inducing membrane ruffling with epidermal growth factor) induced this epithelial cell response. These results indicate that specific interactions between the apical surface of epithelial cells and S. typhimurium, rather than simply bacterial invasion, mediate the epithelial direction of PMN transmigration. To further investigate the means by which S. typhimurium induces epithelia to direct PMN movement, we investigated whether the same signaling pathways regulate secretion of IL-8 and PEEC. IL-8 secretion, but not PEEC secretion, was activated by phorbol myristate acetate and blocked by an inhibitor (mg-132) of the proteosome which mediates NF-kappabeta activation. Further, secretion of IL-8, but not PEEC, was activated by an entry-deficient (HilDelta) S. typhimurium mutant or by basolateral invasion of a wild-type strain. Together, these results indicate that distinct signaling pathways mediate S. typhimurium invasion, induction of IL-8 secretion, and induction of PEEC secretion in model intestinal epithelia.     

Fault-tree analysis for system design, development, modification,and verification

A methodology that uses fault-tree analysis (FTA) techniques to assess the weaknesses of a new chemical/process design at any time during system development is presented. FTA provides a cost-effective means of improving or verifying the reliability and efficiency of chemical/process design. It evaluates the consequences of conceivable failure to indicate where improvements are justified. FTA techniques were used to model the failure modes of an existing control-room heating, ventilation, and air-conditioning (HVAC) system of a large production facility. The fault-tree reduction revealed 129 single-, 434 double-, and 442 triple-failure combinations, any of which could cause system failure. Single failures and double failures consisting of an equipment malfunction and an operator failure error were targeted for design and/or procedural modifications. These modifications were then incorporated into the operating system design to enhance system availability. In an iterative fashion, FTA techniques were reapplied to the modified design and used to verify the adequacy of the proposed revisions prior to implementation. This resulted in a thorough review of system vulnerabilities and a clear understanding of how to correct them     

Cloning and functional expression of a human liver organic cation transporter

OBJECTIVE: The triglyceride-lowering effects of omega-3 fats and HDL cholesterol-raising effects of exercise may be appropriate management for dyslipidemia in NIDDM. However, fish oil may impair glycemic control in NIDDM. The present study examined the effects of moderate aerobic exercise and the incorporation of fish into a low-fat (30% total energy) diet on serum lipids and glycemic control in dyslipidemic NIDDM patients. RESEARCH DESIGN AND METHODS: In a controlled, 8-week intervention, 55 sedentary NIDDM subjects with serum triglycerides > 1.8 mmol/l and/or HDL cholesterol < 1.0 mmol/l were randomly assigned to a low-fat diet (30% daily energy intake) with or without one fish meal daily (3.6 g omega-3/day) and further randomized to a moderate (55-65% VO2max) or light (heart rate < 100 bpm) exercise program. An oral glucose tolerance test (75 g), fasting serum glucose, insulin, lipids, and GHb were measured before and after intervention. Self-monitoring of blood glucose was performed throughout. RESULTS: In the 49 subjects who completed the study, moderate exercise improved aerobic fitness (VO2max) by 12% (from 1.87 to 2.07 l/min, P = 0.0001). Fish consumption reduced triglycerides (0.80 mmol/l, P = 0.03) and HDL3 cholesterol (0.05 mmol/l, P = 0.02) and increased HDL2 cholesterol (0.06 mmol/l, P = 0.01). After adjustment for age, sex, and changes in body weight, fish diets were associated with increases in GHb (0.50%, P = 0.05) and self-monitored glucose (0.57 mmol/l, P = 0.0002), which were prevented by moderate exercise. CONCLUSIONS: A reduced fat diet incorporating one daily fish meal reduces serum triglycerides and increases HDL2 cholesterol in dyslipidemic NIDDM patients. Associated deterioration in glycemic control can be prevented by a concomitant program of moderate exercise.     

Influence of ammonia on the conductivity of Nafion membranes

The effect of NH₃ and NH₄⁺ poisoning on the conductivity of Nafion membranes was investigated via electrochemical impedance spectroscopy. The conductivities of membranes prepared with different NH₄⁺ compositions were measured in deionized water at room temperature and compared to those at 80 °C in a gas phase for various relative humidities. The liquid-phase conductivity decreased linearly with an increase in the NH₄⁺ composition in the membrane (y_NH4⁺), with that of the NH₄⁺-form having a conductivity 25% that of the H⁺-form. The gas-phase conductivity of the NH₄⁺-form, on the other hand, declined by 66–98% relative to the H⁺-form depending on humidity. The conductivities of fresh membranes in the presence of gas-phase NH₃ at different humidities were also studied. The conductivity decreased with time-on-stream and reached the same conductivity at a given humidity regardless of the NH₃ concentration, but the time to reach steady-state varied with NH₃ concentration. The y_NH4⁺ at steady-state conductivity was equivalent for all the NH₃ concentrations studied. The kinetics of conductivity decrease was slower at higher humidities. The humidity and y_NH4⁺ appear to have a concerted effect on the conductivity. The quantitative conductivity data under practical fuel cell conditions should be useful for future fuel cell modeling.