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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.

Critics argue that the modern epidemiologist seems more concerned with intricately modelling complex relationships among risk factors than understanding their origins and their implications for public health. Indeed, some contend that epidemiology has reached its limits as a discipline. To address such concerns, alternatives have been proposed that integrate biological, analytical, and social approaches to epidemiological practice and training.

An algorithm is presented for the identification of aircraft stability derivatives and distributed control derivatives, in real time. Feedback control correlates the effectors' displacement with the aerodynamic angles, while the most commonly used control allocation algorithms correlate the effectors. The result is that valid derivative estimation is not possible. This paper addresses the effector identification problem by including decorrelating excitation into the control allocation cost function while still satisfying the desired control moment, and therefore does not introduce any residual perturbations into the motion variables. A two‐step identification algorithm is used where the stability derivative and a generalized control derivative are identified in the first step. Results are shown for a stability axis roll maneuver with the stability and control derivatives being identified for five differential lateral directional effectors. Published in 1999 by John Wiley & Sons, Ltd. This article is a US Government work and is in the public domain in the United States.

An algorithm is presented for the identification of aircraft stability derivatives and distributed control derivatives, in real time. Feedback control correlates the effectors' displacement with the aerodynamic angles, while the most commonly used control allocation algorithms correlate the effectors. The result is that valid derivative estimation is not possible. This paper addresses the effector identification problem by including decorrelating excitation into the control allocation cost function while still satisfying the desired control moment, and therefore does not introduce any residual perturbations into the motion variables. A two-step identification algorithm is used where the stability derivative and a generalized control derivative are identified in the first step. Results are shown for a stability axis roll maneuver with the stability and control derivatives being identified for five differential lateral directional effectors. Published in 1999 by John Wiley & Sons, Ltd. This article is a US Government work and is in the public domain in the United States.

Summary Two chemically distinct types of hydrogel lenses, vifilcon A and bufilcon A, each with a water content of 55%, were challenged in a balanced salts solution withAspergillus fumigatus, Cladosporium cladosporioides, Curvularia lunata andFusarium solani. The lenses were cleaned, disinfected and stained after varying periods of incubation and examined with light microscopy and scanning electron microscopy. For three of the four fungi, the bufilcon A lens was more susceptible to fungal attack than the vifilcon A lens.Curv. lunata produced the greatest number of penetration pegs within 72 h for both lens types. Etching of lens surfaces was observed withC. cladosporioides. In general, the susceptibility of a hydrogel lens to penetration with a fungus appeared to vary with the species of fungus and the chemical composition of the lens.

In December 1991, US blood centers reported an unusual increase in donations that tested falsely reactive for antibodies to two or more (multiple false positive) of the following viruses: human immunodeficiency virus type 1 (HIV-1), human T-cell lymphotrophic virus type I (HTLV-I), and hepatitis C virus. Many of these donations were from people who had recently received the 1991-1992 influenza vaccine, raising the possibility that this vaccine had somehow specifically caused the problem of multiple false reactivity. A case-control study of 101 affected donors and 191 matched controls found that recent receipt of any brand of influenza vaccine was significantly associated with testing multiple false positive (p < 0.05), as was a history of recent acute illness (p < 0.05) and of allergies (p < 0.05). Surveillance for monthly rates of multiple reactive donations from May 1990 through December 1992 linked the seasonal cluster of multiple false-positive donations to the use of viral screening test kits thought to react nonspecifically to donor immunoglobulin M. There was no similar increase in multiple false-positive donations during the 1992-1993 influenza vaccination season after the HIV-1 and hepatitis C virus tests were replaced; however, the number of donations that were falsely reactive for only HTLV-I almost doubled, indicating that false reactivity was not specifically associated with the 1991-1992 influenza vaccine. Retesting of affected donors found that the duration of HTLV-I and hepatitis C virus false reactivity was 3-6 months. The cluster of multiple false-positive donations in 1991 was most likely caused by the test kits used, rather than by the influenza vaccine.

Filamentous fungi of the genera Acremonium, Aspergillus, Alternaria, Cladosporium, Curvularia, and Fusarium penetrated the matrix of soft contact lenses both during normal usage and in laboratory studies. Growth of the fungi within the lens matrix increased with increasing water content of the lens. Hyphae within the lens were coiled. Some species penetrated completely through the lens within 96 h. More frequent cleaning and disinfection of extended-wear soft contact lenses is recommended.

In a blinded, placebo-controlled study, the reactogenicity, immunogenicity, and clinical efficacy of single doses of US inactivated split-virus and Russian live attenuated, cold-adapted influenza vaccines were compared in 555 schoolchildren in Vologda, Russia. Serial serum samples were collected and school absenteeism was assessed. Systemic reactions were rare, but local reactions (primarily erythema at the injection site) were observed in 27% of the inactivated vaccine group, and coryza (12%) and sore throat (8%) were observed in the attenuated vaccine group. At 4 weeks after vaccination, a 4-fold rise in titer of hemagglutination inhibition antibody to A (H1N1), A (H3N2), and B was noted, respectively, among 78%, 88%, and 53% of children who received inactivated vaccine and among 55%, 79%, and 30% of children who received attenuated vaccine. The vaccine efficacy for preventing school absenteeism due to acute respiratory illness during the period of peak influenza activity was 56% for inactivated vaccine and 47% for attenuated vaccine.