Feedforward model predictive control

This paper examines the role played by feedforward in model predictive control (MPC). We contrast feedforward with preview action. The latter is standard in model predictive control, whereas feedforward has been rarely, if ever, used in contemporary formulations of MPC. We argue that feedforward can significantly improve performance in the presence of measurement noise and certain types of model uncertainty.     

Learning automata-based solutions to the nonlinear fractional knapsack problem with applications to optimal resource allocation.

This paper considers the nonlinear fractional knapsack problem and demonstrates how its solution can be effectively applied to two resource allocation problems dealing with the World Wide Web. The novel solution involves a "team" of deterministic learning automata (LA). The first real-life problem relates to resource allocation in web monitoring so as to "optimize" information discovery when the polling capacity is constrained. The disadvantages of the currently reported solutions are explained in this paper. The second problem concerns allocating limited sampling resources in a "real-time" manner with the purpose of estimating multiple binomial proportions. This is the scenario encountered when the user has to evaluate multiple web sites by accessing a limited number of web pages, and the proportions of interest are the fraction of each web site that is successfully validated by an HTML validator. Using the general LA paradigm to tackle both of the real-life problems, the proposed scheme improves a current solution in an online manner through a series of informed guesses that move toward the optimal solution. At the heart of the scheme, a team of deterministic LA performs a controlled random walk on a discretized solution space. Comprehensive experimental results demonstrate that the discretization resolution determines the precision of the scheme, and that for a given precision, the current solution (to both problems) is consistently improved until a nearly optimal solution is found--even for switching environments. Thus, the scheme, while being novel to the entire field of LA, also efficiently handles a class of resource allocation problems previously not addressed in the literature.     

Flow structure through pool‐riffle sequences and a conceptual model for their sustainability in gravel‐bed rivers

Detailed field measurements and simulations of three‐dimensional flow structure were used to develop a conceptual model to explain the sustainability of self‐formed pool‐riffle sequences in gravel‐bed rivers. The analysis was conducted at the Red River Wildlife Management Area in Idaho, USA, and enabled characterization of the flow structure through two consecutive pool‐riffle sequences, including: identification of jet concentration and dissipation zones, and the development of local turbulence features (i.e. vertical and horizontal eddies) under different flow conditions. Three‐dimensional hydraulic simulations were used to evaluate how the flow structure varies across a range of flow conditions and with different degrees of sediment aggradation within the upstream pool. The analysis demonstrated a significant influence of the residual pool depth on the flow structure, with reduced residual depth causing a shift in the orientation of the jet and a reduction in the influence of vertical eddies and the size and intensity of horizontal eddies. The proposed conceptual model seeks to explain the sustainability of pools in terms of the flow structure in pool‐riffle morphology and how this flow structure will change as a result of altered external forcing, such as upstream sediment delivery or changes in bank stability. Copyright © 2010 John Wiley & Sons, Ltd.     

Creatine kinase isoenzymes in serum from cord blood and the blood of healthy full-term infants during the first three postnatal days

Isoenzymes of creatine kinase (ATP:creatine phosphotransferase; EC 2.7.3.2; CK) were measured by electrophoresis in serum from cord blood and skin-puncture blood taken from 45 healthy full-term infants during the first three postnatal days. Mean total CK activities (in U/L at 30 degrees C) were 185 in cord samples, 536 in samples taken between 5--8 h postnatally, 494 between 24--33 h, and 288 in the 72-100 h samples. Values for all three isoenzymes increased to a peak over this period, with the highest values generally being found in the samples taken 5--33 h after birth; the subsequent decline was most rapid for CK-BB. Serum CK isoenzymes in cord samples and those taken at 72--100 h in the 11 babies delivered by cesarian section did not differ significantly from those of babies delivered vaginally. However the postnatal increases in total CK, CK-MM, and CK-MB (but not in CK-BB) were significantly greater in those patients born by vaginal delivery. The reasons for the increases in CK isoenzymes after birth are not clear, but our results and reported studies on the ontogeny of CK suggest that CK-MB cannot be regarded as a "cardiac-specific" isoenzyme in the neonatal period.     

Magnetic flux array for spontaneous magnetic reconnection experiments

Experimental investigation of reconnection in magnetized plasmas relies on accurate characterization of the evolving magnetic fields. In experimental configurations where the plasma dynamics are reproducible, magnetic data can be collected in multiple discharges and combined to provide spatially resolved profiles of the plasma dynamics. However, in experiments on spontaneous magnetic reconnection recently undertaken at the Versatile Toroidal Facility at MIT, the reconnection process is not reproducible and all information on the plasma must be collected in a single discharge. This paper describes a newly developed magnetic flux array which directly measures the toroidal component of the magnetic vector potential, A(phi). From the measured A(phi), the magnetic field geometry, current density, and reconnection rate are readily obtained, facilitating studies of the three-dimensional dynamics of spontaneous magnetic reconnection. The novel design of the probe array allows for accurate characterization of profiles of A(phi) at multiple toroidal angles using a relatively small number of signal channels and with minimal disturbance of the plasma.     

Performance evaluation of canine-associated Bacteroidales assays in a multi-laboratory comparison study

The contribution of fecal pollution from dogs in urbanized areas can be significant and is an often underestimated problem. Microbial source tracking methods (MST) utilizing quantitative PCR of dog-associated gene sequences encoding 16S rRNA of Bacteroidales are a useful tool to estimate these contributions. However, data about the performance of available assays are scarce. The results of a multi-laboratory study testing two assays for the determination of dog-associated Bacteroidales (DogBact and BacCan-UCD) on 64 single and mixed fecal source samples created from pooled fecal samples collected in California are presented here. Standardization of qPCR data treatment lowered inter-laboratory variability of sensitivity and specificity results. Both assays exhibited 100% sensitivity. Normalization methods are presented that eliminated random and confirmed non-target responses. The combination of standardized qPCR data treatment, use of normalization via a non-target specific Bacteroidales assay (GenBac3), and application of threshold criteria improved the calculated specificity significantly for both assays. Such measures would reasonably improve MST data interpretation not only for canine-associated assays, but for all qPCR assays used in identifying and monitoring fecal pollution in the environment.     

Multi-laboratory evaluations of the performance of Catellicoccus marimammalium PCR assays developed to target gull fecal sources

Here we report results from a multi-laboratory (n = 11) evaluation of four different PCR methods targeting the 16S rRNA gene of Catellicoccus marimammalium originally developed to detect gull fecal contamination in coastal environments. The methods included a conventional end-point PCR method, a SYBR^® Green qPCR method, and two TaqMan^® qPCR methods. Different techniques for data normalization and analysis were tested. Data analysis methods had a pronounced impact on assay sensitivity and specificity calculations. Across-laboratory standardization of metrics including the lower limit of quantification (LLOQ), target detected but not quantifiable (DNQ), and target not detected (ND) significantly improved results compared to results submitted by individual laboratories prior to definition standardization. The unit of measure used for data normalization also had a pronounced effect on measured assay performance. Data normalization to DNA mass improved quantitative method performance as compared to enterococcus normalization. The MST methods tested here were originally designed for gulls but were found in this study to also detect feces from other birds, particularly feces composited from pigeons. Sequencing efforts showed that some pigeon feces from California contained sequences similar to C. marimammalium found in gull feces. These data suggest that the prevalence, geographic scope, and ecology of C. marimammalium in host birds other than gulls require further investigation. This study represents an important first step in the multi-laboratory assessment of these methods and highlights the need to broaden and standardize additional evaluations, including environmentally relevant target concentrations in ambient waters from diverse geographic regions.     

A nuclear-encoded intein in the fungal pathogen Cryptococcus neoformans.

We have used comparative sequence analysis to identify an intein-like sequence (protein splicing element) present in Cryptococcus neoformans, a fungal pathogen of humans. The sequence encoding this element is present in the C. neoformans PRP8 gene, as an in-frame insertion relative to the PRP8 genes of other organisms. It contains sequences similar to those of the protein-splicing domains of two previously described yeast inteins (in Saccharomyces cerevisiae and Candida tropicalis), although it lacks any recognizable internal endonuclease domain. The Cryptococcus neoformans intein (Cne PRP8) is only the second to be found in a eukaryote nuclear genome; the previously described yeast inteins occur at the same site in the VMA gene homologues of S. cerevisiae and C. tropicalis. The host gene of the Cryptococcus intein, PRP8, encodes a highly conserved mRNA splicing protein found as part of the spliceosome. The Cne PRP8 intein may be a useful drug target in addressing the cryptococcal infections so prevalent in AIDS patients.