Limitations of disturbance rejection in feedback systems withfinite bandwidth

Studies limitations of disturbance rejection in closed-loop control systems. The disturbance is modeled as colored noise, and disturbance rejection is measured by the output variance. Lower bounds on the achievable output variance are derived under several practical constraints, the main one being a bound on the system bandwidth; constraints on the stability robustness (measured by the distance from the Nyquist plot to the critical point) and the ability to track low-frequency reference signals (measured by the sensitivity reduction at low frequencies) are also considered. The bounds are derived by finding the sensitivity function that minimizes the output variance. This optimization is performed subject to the above constraints and, in addition, subject to certain sensitivity integral constraints that arise because of closed-loop stability. The utility of the results is illustrated by analyzing the achievable level of passenger comfort in an aircraft subjected to turbulence     

Monoclonal and polyclonal antibodies to chicken immunoglobulin isotypes specifically detect turkey immunoglobulin isotypes

Turkey immunoglobulin (Ig) isotypes IgG and IgM were isolated from blood and IgA was isolated from bile. Isolation was accomplished by gel filtration of the ammonium sulphate cut on Sephacryl S-200. Using immunoelectrophoresis and indirect ELISA, the cross-reactivity between antibodies, of monoclonal and polyclonal origin, specific for the Ig isotypes of chicken, and the purified turkey Ig isotypes was evaluated. Commercially available polyclonal antibodies, anti-chicken/IgA (alpha-chain specific, affinity purified), anti-chicken/IgG (Fc-fragment specific) and anti-chicken/IgM (mu-chain specific) showed an interspecies cross-reactivity with the corresponding turkey Ig isotypes. The monoclonal antibody (MAb) AV-G3 specifically detected turkey IgG, whereas MAb M1 reacted exclusively with turkey IgM. This panel of anti-immunoglobulins represents a useful tool for examining the humoral immune responses of turkeys.     

Assessment of nutritional status in CAPD patients: serum albumin is not a useful measure

INTRODUCTION: In CAPD patients serum albumin is frequently used as an index of nutritional status, although it is recognized that hypoalbuminaemia may be caused by many factors. We have further examined the relationship between serum albumin and nutrition. METHODS: Nutritional status was assessed by biochemistry, anthropometry, mid-arm muscle circumference, muscle strength (hand grip and back), and lean body mass (from anthropometry, creatinine kinetics and bioimpedance) in a group of 76 stable CAPD patients. Correlations between biochemical and nutritional parameters were sought and data were compared between patient groups defined by serum albumin (> or = 37 vs < 37 g/l on two occasions 2 months apart) and separately according to subjective global assessment score (normal nutrition, A vs mild to moderate, B, and severe, C, malnutrition). RESULTS: In patients with a low SGA score, actual body weight, body mass index, mid-arm muscle circumference, lean body mass, subscapular skinfold thickness, hand grip strength (males and females) and iliac and triceps skinfold thicknesses and back strength (females only) were all significantly less than in patients with a normal SGA score. In contrast, none of these variables differed in either gender when patients were compared according to serum albumin. Serum albumin was correlated with serum creatinine (r = 0.45, P = 0.01), daily urine protein excretion (r = -0.42, P = 0.02) and uncorrected weekly creatinine clearance (r = -0.39) in females, but not with any index of body composition in either gender. CONCLUSION: Whilst SGA identified a patient group with significantly abnormal body mass, muscle mass and muscle strength, serum albumin did not. Serum albumin is not a useful marker of malnutrition in stable patients on CAPD.     

PHYSICAL PROPERTIES OF ASPHALT-RUBBER BINDER

This study was performed to determine how the rheological properties of asphalt-rubber binders are affected by various parameters. Properties studied were asphalt composition, rubber dissolution, and the low-, intermediate-, and high-temperature rheological properties, measured with the bending beam rheometer. dynamic shear rheometer, and rotational viscometer, respectively. The rheological properties of the asphalt-rubber binder were determined to be dependent on the rubber content (weight percent), rubber particle size, and base asphalt composition. By controlling these variables, an asphalt-rubber binder with improved low-temperature cracking resistance, improved mid-temperature rutting resistance and temperature susceptibility, and a non-detrimental high-temperature compaction viscosity, all relative to the base asphalt, can be produced.     

Peak bone mineral accrual and age at menarche in adolescent girls: a 6-year longitudinal study

To study the effect of a high radiation background on the structure and function of the T-complex, we used laboratory mice carrying t-haplotypes of four complementation groups (t0, t12, tw1, and tw5). In 1987-1989, the animals were kept each year for a month within a 30-kilometer zone of Chernobyl Nuclear Power Station in regions with different degrees of pollution. Subsequent genetic analysis revealed a decrease in fertility, fecundity, and the index of preferable transmission of t-carrying chromosomes in radiated animals and some of their progeny. The effect of different radiation doses on these parameters was different in animals with various t-haplotypes. A lack of complementation or a decrease in the complementation effect was revealed in a number of crosses involving the progeny of irradiated animals. The frequency of complementation distortion was about 8 x 10(-2), which is more than an order higher than the usual recombination frequency characteristic of these t-haplotypes.     

A surgical model for determination of true absorption and biliary excretion of manganese in conscious swine fed commercial diets

Some trace elements, such as Mn, Cu and Zn, are absorbed and quickly resecreted into the gut through the bile. When this occurs, the unabsorbed nutrient and the absorbed and resecreted nutrient may mix in the gut, preventing quantitative calculation of either. We have developed a surgical model that prevents this complication. Pigs (20-40 kg) were fitted with cannulas in the bile duct, lumen of the duodenum, portal vein, ileocolic vein and jugular vein. After recovery for 6-8 d, pigs were given an oral dose of 9.25 mBq of 54Mn. The flow rate of blood past the portal vein was determined by infusion of P-amino hippuric acid into the ileocolic vein. Absorption was quantified by multiplying the concentration of 54Mn in the portal blood by the flow rate. Biliary excretion was determined by quantitative collection of bile, and previously collected bile was reinfused into the gut lumen. Urine and feces were also quantitatively collected. A postoperative time of 6-8 d was sufficient for pigs to recover from the effects of surgery and anesthesia, as assessed by several measures of metabolic function and food and water intake. True absorption was calculated to be 0.5%. 54Mn in the urine and bile began to increase after 4 d. When the pigs were killed after 12 d, only 0.5% of the 54Mn remained in the carcass. Results of this study show that pigs surgically modified by the described procedure can recover fully and can serve as a model to study intestinal absorption and biliary excretion of nutrients. Furthermore, initial studies using 54Mn showed that the model is applicable to studying Mn metabolism and suggest the need for a more detailed study of Mn absorption and biliary excretion.     

Incremental Validity of the Frame-of-Reference Effect in Personality Scale Scores: A Replication and Extension.

Context-specific personality items provide respondents with a common frame of reference unlike more traditional, noncontextual personality items. The common frame of reference standardizes item interpretation and has been shown to reduce measurement error while increasing validity in comparison to noncontextual items (M. J. Schmit, A. M. Ryan. S. L. Stierwalt. & S. L. Powell, 1995). Although the frame-of-reference effect on personality scales scores has been well investigated (e.g., M. J. Schmit et al., 1995), the ability of this innovation to obtain incremental validity above and beyond the well-established, noncontextual personality scale scores has yet to be examined. The current study replicates and extends work by M. J. Schmit et al. (1995) to determine the incremental validity of the frame-of-reference effect. The results indicate that context-specific personality items do indeed obtain incremental validity above and beyond both noncontextual items and cognitive ability, and in spite of socially desirable responding induced by applicant instructions. The implications of these findings for personnel selection are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)