Implications of spatial aggregation of parasites for the population dynamics in host-parasite interaction

Some aspects of the widely observed over-dispersed pattern of the distribution of parasites within the host population are examined. It has been established in the parasitological literature that most hosts usually harbour few parasites, while only few hosts harbour a large proportion of the parasite population. Factors that may influence the pattern of distribution of parasites, the relation between the level of parasite aggregation and the prevalence of infection, and changes in this level of aggregation as a function of host age are analysed. Factors which determine the diversity of species in parasite communities are presented, and aspects of exploitative and interference competition among parasites and their relations with biological control procedures are also considered. Attention is also focused on the regulatory and destabilizing processes influencing the dynamic behaviour of host-parasite population interactions.     

Analysis of left ventricular wall motion based on volumetric deformable models and MRI-SPAMM

We present a new approach for the analysis of the left ventricular shape and motion based on the development of a new class of volumetric deformable models. We estimate the deformation and complex motion of the left ventricle (LV) in terms of a few parameters that are functions and whose values vary locally across the LV. These parameters capture the radial and longitudinal contraction, the axial twisting, and the long-axis deformation. Using Lagrangian dynamics and finite-element theory, we convert these volumetric primitives into dynamic models that deform due to forces exerted by the datapoints. We present experiments where we used magnetic tagging (MRI-SPAMM) to acquire datapoints from the LV during systole. By applying our method to MRI-SPAMM datapoints, we were able to characterize the 3-D shape and motion of the LV both locally and globally, in a clinically useful way. In addition, based on the model parameters we were able to extract quantitative differences between normal and abnormal hearts and visualize them in a way that is useful to physicians.     

Aging, expertise, and narrative processing.

In a study of how aviation expertise influences age differences in narrative processing, young and older pilots and nonpilots read and recalled aviation and general narratives. They chose referents for sentences referring to a protagonist or minor character mentioned 1 sentence (recent character) or 3 sentences (distant character) before this target sentence. All groups chose referents less accurately for sentences about distant and minor characters than about recent and protagonist characters, perhaps because these referents were less likely to be in working memory. Young readers and pilots were more accurate for distant and minor character target sentences in aviation narratives and recalled aviation narratives more accurately. Expertise did not reduce age differences. Expertise differences may reflect decreased demands on working memory capacity, and age declines may reflect reduced capacity. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

pH and salt responsive poly(N,N-dimethylaminoethyl methacrylate) cylindrical brushes and their quaternized derivatives

We present the synthesis and characterization of poly(N,N-dimethylaminoethyl methacrylate) (PDMAEMA) cylindrical brushes, their pH responsiveness, and the corresponding quaternized analog, poly{[2-(methacryloyloxy)ethyl] trimethylammonium iodide} (PMETAI) brushes. PDMAEMA brushes were prepared by atom transfer radical polymerization (ATRP) using the grafting-from strategy. Initiating efficiencies of the ATRP processes were determined by cleaving the side-chains and gel permeation chromatography (GPC) analysis. Due to the slow initiation and steric hindrance, the initiating efficiency is only around 50%. The PDMAEMA brushes show worm-like structures and pH responsiveness, as proven by dynamic light scattering (DLS), atomic force microscopy (AFM), and cryogenic transmission electron microscopy (cryo-TEM) measurements. Strong cationic polyelectrolyte PMETAI brushes were produced by quaternization of the PDMAEMA brushes. AFM and cryo-TEM images showed similar worm-like morphologies for the PMETAI brushes. The PMETAI brushes collapsed in solution with high concentration of monovalent salt, as proven by DLS and AFM results.     

Decision support in early development phases—A case study from machine engineering

In the case study presented in this paper we consider early development phases of a mechanical product. We want to evaluate different concepts and decide which one(s) to pursue. A problem in early phases is that usually no test runs are available. In our case study, based on a standard, there are ways to compute the lifetime distributions of the components of the different concepts. Some parameters needed for these computations are not known precisely. Unfortunately, the lifetime distributions of the components are highly sensitive to these parameters. Our approach is to equip these parameters with distributions. These distributions would be called prior distributions in Bayesian terminology, but no update is possible since no test runs are available. Our approach implies that the distribution of the system lifetime for each concept is random, i.e. we get random elements in the space of lifetime distributions. Using Monte-Carlo simulations, we demonstrate several ways to compare the random lifetime distributions of the concepts. Some of these comparisons use stochastic orderings. We also introduce a new stochastic ordering which is particularly suitable for reliability purposes. Our case study, consisting of three scenarios, allows us to demonstrate some conclusions that can be reached.     

Emission Of Volatile And Semivolatile Organic Compounds From Waterborne Paints – The Effect Of The Film Thickness

A waterborne paint was applied to tin plated steel sheets with three different film thicknesses. The emission of volatile and semivolaile organic compounds ((S) VOCs) from the samples was measured in small climatic chambers under standard conditions over a two-week period. The purpose of the study was to evaluate the effect of the film thickness on the emission rate decay. First order decay models, including sink effects for the high boiling (S) VOCs, were fitted to the concentration versus time data. The results showed that the first order rate constants decrease with increasing film thickness. In uddition, the results indicated that the emissions of the (S)VOCs in the waterborne paint film seemed to be controlled by evaporation. The thicknesses of paint films used in climatic chamber tests to estimate emission rates for product compurison or emission prediction must be known in order to prevent erroneous conclusions     

The efficacy and cost effectiveness of vaccination against influenza among elderly persons living in the community

BACKGROUND: Despite recommendations for annual vaccination against influenza, more than half of elderly Americans do not receive this vaccine. In a serial cohort study, we assessed the efficacy and cost effectiveness of influenza vaccine administered to older persons living in the community. METHODS: Using administrative data bases, we studied men and women over 64 years of age who were enrolled in a large health maintenance organization in the Minneapolis-St. Paul area. We examined the rate of vaccination and the occurrence of influenza and its complications in each of three seasons: 1990-1991, 1991-1992, and 1992-1993. Outcomes were adjusted for age, sex, diagnoses indicating a high risk, use of medications, and previous use of health care services. RESULTS: Each cohort included more than 25,000 persons 65 years of age or older. Immunization rates ranged from 45 percent to 58 percent. Although the vaccine recipients had more coexisting illnesses at base line than those who did not receive the vaccine, during each influenza season vaccination was associated with a reduction in the rate of hospitalization for pneumonia and influenza (by 48 to 57 percent, P < or = 0.002) and for all acute and chronic respiratory conditions (by 27 to 39 percent, P < or = 0.01). Vaccination was also associated with a 37 percent reduction (P = 0.04) in the rate of hospitalization for congestive heart failure during the 1991-1992 season, when influenza A was epidemic. The costs of hospitalization for all types of illness studied were lower in the vaccinated group during 1991-1992 (range of reduction, 47 to 66 percent; P < 0.005) and for acute and chronic respiratory conditions and congestive heart failure in 1990-1991 (reductions of 37 percent and 43 percent, respectively; P < or = 0.05). Direct savings per year averaged $117 per person vaccinated (range, $21 to $235), with cumulative savings of nearly $5 million. Vaccination was also associated with reductions of 39 to 54 percent in mortality from all causes during the three influenza seasons (P < 0.001). CONCLUSIONS: For elderly citizens living in the community, vaccination against influenza is associated with reductions in the rate of hospitalization and in deaths from influenza and its complications, as compared with the rates in unvaccinated elderly persons, and vaccination produces direct dollar savings.