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Selected AbstractsApproximate dynamic programming based optimal control applied to an integrated plant with a reactor and a distillation column with recycleAICHE JOURNAL, Issue 4 2009Thidarat Tosukhowong Abstract An approximate dynamic programming (ADP) method has shown good performance in solving optimal control problems in many small-scale process control applications. The offline computational procedure of ADP constructs an approximation of the optimal "cost - to - go" function, which parameterizes the optimal control policy with respect to the state variable. With the approximate "cost - to - go" function computed, a multistage optimization problem that needs to be solved online at every sample time can be reduced to a single-stage optimization, thereby significantly lessening the real-time computational load. Moreover, stochastic uncertainties can be addressed relatively easily within this framework. Nonetheless, the existing ADP method requires excessive offline computation when applied to a high-dimensional system. A case study of a reactor and a distillation column with recycle was used to illustrate this issue. Then, several ways were proposed to reduce the computational load so that the ADP method can be applied to high-dimensional integrated plants. The results showed that the approach is much more superior to NMPC in both deterministic and stochastic cases. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] A new laser pain threshold model detects a faster onset of action from a liquid formulation of 1 g paracetamol than an equivalent tablet formulationBRITISH JOURNAL OF CLINICAL PHARMACOLOGY, Issue 1 2002J. A. Sutton Aims, To discover whether a new infra-red laser method could detect a change in pain threshold after as mild an analgesic as paracetamol and whether an effervescent liquid formulation produced a faster onset of action than tablets. Methods,This double-blind, placebo controlled randomized study used a portable, infra-red laser to measure ,first pain' thresholds on the nondominant forearm in 12 normal volunteers before and after 1 g of paracetamol or placebo. The mean of six recordings was determined three times before dosing, the first being used as a familiarization procedure, and 14 times after dosing. Results,We detected a small (2%), statistically significant difference in pain threshold between a liquid formulation of paracetamol and placebo at 30 and 60 min (P = 0.004 and P = 0.001), but not between tablets and placebo. Liquid also increased the threshold significantly compared with tablets at 60 min (P = 0.01). Conclusions,To detect such a small increase in pain threshold requires a highly consistent measure and the coefficient of variation was 2% for the study overall, surprisingly low for a subjective phenomenon. The reasons for this include minimizing reflectance by blacking the skin, using a nonhairy site, averaging six data points at each sample time and controlling closely the ambient conditions and the subjects' preparation for studies. [source] Chronic shedding of Campylobacter species in beef cattleJOURNAL OF APPLIED MICROBIOLOGY, Issue 2 2004G.D. Inglis Abstract Aims:, To determine the prevalence of chronic shedding of Campylobacter species by beef cattle, a longitudinal study of shedding patterns was conducted in a cohort of 60 beef steers over a 4-month period. Methods and Results:, Steers were maintained in a simulated feedlot setting but individually in pens to minimize transmission among animals. At each collection time, campylobacters in faeces were detected using conventional PCR. In addition, quantities of Campylobacter jejuni and C. lanienae in faeces were measured using real-time quantitative (RTQ) PCR. All of the steers tested shed Campylobacter species during the course of the study, and overall, 90% of the 299 samples tested were positive for Campylobacter DNA. The majority of the animals (86%) shed campylobacters at ,4 sample times. The most prevalent taxon detected in bovine faeces was C. lanienae (56% of samples) followed by C. jejuni (13%), C. hyointestinalis (8%), and C. fetus (2%). No C. coli was detected, and 13% of the faecal samples contained two or more of the above species. Seven (12%) and 34 (57%) animals shed C. jejuni and C. lanienae at ,3 sample times, respectively. For both C. lanienae and C. jejuni, a substantial number of cells were detected in faeces using RTQ-PCR; 27% of the samples positive for C. jejuni contained populations >104 cells g,1 (maximum of 5 × 105 cells g,1), and 44% of samples positive for C. lanienae possessed populations >106 cells g,1 (maximum of 4 × 108 cells g,1). A significant correlation was observed between shedding of C. lanienae and the severity of liver abscesses. In 27% of the samples, an amplicon was obtained for genus-specific but not for the species-specific primers. Sequencing of the partial 16S rRNA gene suggested the presence of at least two undescribed Campylobacter species but this has yet to be confirmed. Conclusions:, A high percentage of feedlot cattle shed large quantities of Campylobacter species in their faeces over a protracted period of time (ca 112 days). Significance and Impact of the Study:, This is the first study of longitudinal shedding patterns of campylobacters in beef cattle using PCR-detection methods. In addition, this is the first use of RTQ-PCR to directly quantify C. jejuni or C. lanienae in faeces. The results of the study show that a large number of cattle (>85%) chronically shed campylobacters in feedlots. [source] Possible biphasic changes of free radicals in ethylene glycol-induced nephrolithiasis in ratsBJU INTERNATIONAL, Issue 9 2000H.S. Huang Objective To evaluate the possible role of free radicals in nephrolithiasis in rats induced by ethylene glycol, and to examine the correlation between the urinary enzymes N-acetyl-,-glucosaminidase (NAG), ,-galactosidase (GAL) and neutral endopeptidase (NEP), and free radical production. Materials and methods Hyperoxaluria was produced in male Wistar rats by adding ethylene glycol to their drinking water. After 7, 21 and 42 days of treatment, urinary oxalate, creatinine clearance and urinary enzymes (NAG, GAL and NEP) were measured. The nitroblue tetrazolium perfusion method was used to locate the sites of free-radical production. Ultrasensitive chemiluminescence was used to directly measure the production of reactive oxygen species (ROS) in vivo. Vitamin E and potassium citrate were fed to rats, in addition to ethylene glycol, to assess their effects on free radical production. Results Urinary oxalate increased significantly and was associated with an increase in NAG and GAL at all sample times. However, urinary NEP activity was unchanged on day 7, although there was four times as much NEP on days 21 and 42 than in the control groups. Formazan particles in the renal cortex were scored as 3+ to 4+ in rats treated for 7 days with ethylene glycol. Blood ROS levels were also higher in this group than in the controls (P < 0.01). After vitamin E and potassium citrate treatment, blood ROS levels were lower than in rats treated with ethylene glycol alone. Conclusion Free radicals may be produced in the early stages of nephrolithiasis in rats fed with ethylene glycol. Free radicals occurred mainly in blood and might be associated with NEP inactivation. [source] | ||||||||||