Minimum-state realizations of linear time-varying systems

An algorithm for removing uncontrollable (unobservable) state variables from time-varying systems is presented. The algorithm makes use of the time-variable controllability (observability) matrix which is augmented with the identity matrix and transformed into Hermite normal form. In this new set of coordinates, the uncontrollable (unobservable) state variables are easily identified and removed. An example is given.     

The Mechanism of Anti-Squawk Additive Behavior in Automatic Transmission Fluids

A theory of anti-squawk additive behavior was formulated based on diffusion and boundary lubricant formation. Friction tests were run with common friction surfaces in a common white paraffin oil containing different anti-squawk additives and analyzed to evaluate the theory. The data indicated dynamic friction was diffusion controlled at any given additive concentration. Additive concentration was not controlling dynamic friction at concentrations above 0.001 moles per liter, although the dynamic frictional behavior of zinc stearate solutions was concentration dependent below 0.001 moles per liter. Static friction data for zinc stearate followed a Langmuir adsorption isotherm. Friction changes caused by boundary lubricants were proportional to the amount of boundary lubricant on the friction surfaces.     

Clarifier Scum Removal Can Be Both Simple and Efficient

The presence of floating scum and trash has troubled many wastewater treatment facilities. These accumulations on circular primary clarifiers, secondary clarifiers, and sludge thickeners are an unsightly nuisance, reduce performance, and cause odors. The added Operation and Maintenance effort—sometimes unsuccessful—can cause a deterioration of the staff morale and adversely impact other plant operations. Skimmers have become more complex and costly, full radial and ducking types, in an attempt to solve these problems. However, a review of conventional scum skimmers revealed that they were not optimized to ensure that flotables could be rapidly moved to the scum ramp/trough. The common problems were low angles of attack of the skimmer, undersized ramps for scum removal, and adverse effects of wind. The recommended skimmer has a bend at a radial point which results in a 25–30° angle of attack and 200–300% higher transport capacity than the tangential skimmer. The paper provides a methodology to establish the quantity of flotables to be removed, design of the bent skimmer and sizing of the scum ramp/trough in a series of tables and graphs.     

Comparative rates of androgen production and metabolism in Caucasian and Chinese subjects

Clinically apparent prostate cancer occurs more commonly among Caucasians living in Western countries than in Chinese in the Far East. Prior studies demonstrated diminished facial and body hair and lower levels of plasma 3 alpha-androstanediol glucuronide and androsterone glucuronide in Chinese than in Caucasian men. Based upon these findings, investigators postulated that Chinese men could have diminished 5 alpha-reductase activity with a resultant decrease in prostate tissue dihydrotestosterone levels and clinically apparent prostate cancer. An alternative hypothesis suggests that decreased 3 alpha-androstanediol glucuronide and androsterone glucuronide levels might reflect reduced production of androgenic ketosteroid precursors as a result of genetic or environmental factors. The present study examined 5 alpha-reductase activity, androgenic ketosteroid precursors, and the influence of genetic and environmental/dietary factors in groups of Chinese and Caucasian men. We found no significant differences in the ratios of 5 beta-:5 alpha-reduced urinary steroids (a marker of 5 alpha-reductase activity) between Chinese subjects living in Beijing, China, and Caucasians living in Pennsylvania. To enhance the sensitivity of detection, we used an isotopic kinetic method to directly measure 5 alpha-reductase activity and found no difference in testosterone to dihydrotestosterone conversion ratios between groups. Then, addressing the alternative hypothesis, we found that the Caucasian subjects excreted significantly higher levels of individual and total androgenic ketosteroids than did their Chinese counterparts. To distinguish genetic from environmental/dietary factors as a cause of these differences, we compared Chinese men living in Pennsylvania and a similar group living in Beijing, China. We detected a reduction in testosterone production rates and total plasma testosterone and sex hormone-binding levels, but not in testosterone MCRs in Beijing Chinese as a opposed to those living in Pennsylvania. Comparing Pennsylvania Chinese with their Caucasian counterparts, we detected no significant differences in total testosterone, free and weakly bound testosterone, sex hormone-binding globulin levels, and testosterone production rates. Taken together, these studies suggest that environmental/dietary, but not genetic, factors influence androgen production and explain the differences between Caucasian and Chinese men.     

Pharmacologic adjuncts to mechanical ventilation in acute respiratory distress syndrome

This article reviews pharmacologic approaches to treating acute respiratory distress syndrome (ARDS). The authors discuss the therapeutic effects of ketoconazole, antioxidants, corticosteroids, surfactant, ketanserin, pentoxifylline, bronchodilators, and almitrine in ARDS. Current animal data and proposed mechanics which may foster future pharmacologic therapies are also examined.     

Growth and survival of Helicobacter pylori in defined medium and susceptibility to Brij 78

The gastrointestinal pathogen Helicobacter pylori requires supplementation with either fetal calf serum (FCS), bovine serum albumin (BSA), or (2,6-dimethyl)-beta-cyclodextrin (CD) for growth in a complex or defined medium. Because the availability of medium in which all components were chemically defined would facilitate metabolic studies of H. pylori, growth of the type strain, ATCC 43504, was compared in a defined medium with different growth additives. The dependency of H. pylori growth on FCS or BSA in a defined medium could partially be replaced by dependency on CD and cholesterol when the last two components were both added to the defined medium. Growth and cell yield were not affected by the addition of glucose, but the culture viability (numbers of CFU per milliliter was extended. Because therapeutic antifoams are used to relieve gastrointestinal symptoms we studied whether the unique susceptibility of H. pylori to the emulsifier polyoxyethylene-20-stearylether (Brij 78) was growth dependent or medium specific. The bactericidal activity exerted in buffer at pH 5 was independent of the preculture medium, and a 5-h exposure of the bacteria to 1.28 to 2.56 microg of Brij 78 per ml reduced the numbers of viable bacteria by >5 log10. The MICs (0.16 to 0.32 microg/ml) were lower than the corresponding minimal bactericidal concentrations in different growth media and were affected by FCS or BSA. In conclusion, CD plus cholesterol promotes the growth of H. pylori in a serum-free defined medium in which glucose enhances cell viability. The antibacterial activity exerted by Brij 78 is neither growth dependent nor medium specific.     

Top Food Sources Contributing to Vitamin D Intake and the Association of Ready-to-Eat Cereal and Breakfast Consumption Habits to Vitamin D Intake in Canadians and United States Americans

Abstract: This study aimed to determine dietary vitamin D intake of U.S. Americans and Canadians and contributions of food sources to total vitamin D intake. Total of 7‐ or 14‐d food intake data were analyzed for vitamin D by a proprietary nutrient assessment methodology that utilized food intake data from the Natl. Eating Trends^® service, portion size data from NHANES 1999–2004, and nutrient values using the Univ. of Minnesota's Nutrition Data System for Research software. Study participants were 7837 U.S. Americans and 4025 Canadians, ≥2‐y‐old males and females. The main outcome measures were total dietary vitamin D intake, percent contribution of foods to total vitamin D intake, and vitamin D intake by cereal and breakfast consumption habits. ANOVA was used to determine differences in means or proportions by age and gender and according to breakfast consumption habits. Mean vitamin D intake ranged from 152 to 220 IU/d. Less than 2% of participants in all age groups from the United States and Canada met the 2011 Recommended Daily Allowance (RDA) for vitamin D from foods. Milk, meat, and fish were the top food sources for vitamin D for both Americans and Canadians. Ready‐to‐eat (RTE) cereal was a top 10 source of vitamin D for Americans but not Canadians. Vitamin D intake was higher with more frequent RTE cereal and breakfast consumption in both countries, largely attributable to greater milk intake. Practical Application: Most U.S. Americans and Canadians do not meet the 2011 Inst. of Medicine recommended daily allowance (RDA) for vitamin D for their age groups from foods. Increasing breakfast and cereal consumption may be a useful strategy to increase dietary vitamin D intake to help individuals meet the RDA for vitamin D, particularly by increasing milk intake. However, it is likely that additional food fortification or vitamin D supplementation is required to achieve the RDA.