Rapid redistribution of clathrin onto macrophage plasma membranes in response to Fc receptor-ligand interaction during frustrated phagocytosis.

We have observed increases in assembled clathrin on the plasma membrane during "frustrated phagocytosis," the spreading of macrophages on immobilized immune complexes. Resident macrophages freshly harvested from the peritoneal cavity of mice and attached to bovine serum albumin (BSA)-anti-BSA-coated surfaces at 4 degrees C had almost no clathrin basketworks on their adherent plasma membrane (less than 0.01 coated patch/micron 2), as observed by immunofluorescence, immunoperoxidase, and platinum-carbon replica techniques, although abundant assembled clathrin was observed in the perinuclear Golgi region. When the cells were warmed to 37 degrees C they started to spread by 4 min and reached their maximum extent by 20 min. Spreading preceded clathrin assembly at the plasma membrane. Clathrin-coated patches were first observed on the adherent plasma membrane at 6 min. Between 12 and 20 min assembled clathrin coats appeared on both adherent and nonadherent plasma membranes with a concomitant decrease in identifiable clathrin in the perinuclear region. A new steady state emerged by 2 h, as perinuclear clathrin began to reappear. At 20 min at 37 degrees C the adherent plasma membranes of macrophages spreading on BSA alone had 0.9 coated patch/micron 2, whereas in cells spread on immune complex-coated surfaces, the clathrin patches increased, dependent on ligand concentration, to a maximum of 2.1 coated patches/micron 2. Because frustrated phagocytosis of immune complex-coated surfaces at 37 degrees C increased the area of adherent plasma membrane, the total area coated by clathrin basket-works increased 5-fold (28 micron 2/cell) as compared with cells plated on BSA alone (5.6 micron 2/cell) and 200-fold as compared with cells adhering to immune complexes at 4 degrees C. We then determined that macrophages cultured on BSA-coated coverslips for 24 h already have abundant surface clathrin. When immune complexes were formed by the addition of anti-BSA IgG to already spread macrophages cultured on BSA-coated coverslips for 24 h, clathrin assembled at the sites of ligand-receptor interaction even at 4 degrees C, before spreading, and a 2.6-fold increase in assembled clathrin was observed on the adherent plasma membrane of cells on immune complexes as compared with cells on BSA alone. Clathrin was reversibly redistributed to the Golgi region, returning to the steady state by 2 h.(ABSTRACT TRUNCATED AT 400 WORDS

Personal Autonomic Computing Reflex Reactions and Self-Healing

The overall goal of this research is to improve theself-awareness and environment-awareness aspect of personal au-tonomic computing (PAC) to facilitate self-managing capabilitiessuch as self-healing. Personal computing offers unique challengesfor self-management due to its multiequipment, multisituation, andmultiuser nature. The aim is to develop a support architecture formultiplatform working, based on autonomic computing conceptsand techniques. Of particular interest is collaboration among per-sonal systems to take a shared responsibility for self-awareness andenvironment awareness. Concepts mirroring human mechanisms,such as reflex reactions and the use ofvital signsto assess oper-ational health, are used in designing and implementing the PACarchitecture. As proof of concept, this was implemented as a self-healing tool utilizing a pulse monitor and a vital signs health moni-tor within the autonomic manager. This type of functionality opensnew opportunities to provide self-configuring, self-optimizing, andself-protecting, as well as self-healing autonomic capabilities topersonal computing

Failure of Intuition When Choosing Whether to Invest in a Single Goal or Split Resources Between Two Goals

In a series of related experiments, we asked people to choose whether to split their attention between two equally likely potential tasks or to prioritize one task at the expense of the other. In such a choice, when the tasks are easy, the best strategy is to prepare for both of them. As difficulty increases beyond the point at which people can perform both tasks accurately, they should switch strategy and focus on one task at the expense of the other. Across three very different tasks (target detection, throwing, and memory), none of the participants switched their strategy at the correct point. Moreover, the majority consistently failed to modify their strategy in response to changes in task difficulty. This failure may have been related to uncertainty about their own ability, because in a version of the experiment in which there was no uncertainty, participants uniformly switched at an optimal point

The role of attention in eye-movement awareness

People are unable to accurately report on their own eye movements most of the time. Can this be explained as a lack of attention to the objects we fixate? Here, we elicited eye-movement errors using the classic oculomotor capture paradigm, in which people tend to look at sudden onsets even when they are irrelevant. In the first experiment, participants were able to report their own errors on about a quarter of the trials on which they occurred. The aim of the second experiment was to assess what differentiates errors that are detected from those that are not. Specifically, we estimated the relative influence of two possible factors: how long the onset distractor was fixated (dwell time), and a measure of how much attention was allocated to the onset distractor. Longer dwell times were associated with awareness of the error, but the measure of attention was not. The effect of the distractor identity on target discrimination reaction time was similar whether or not the participant was aware they had fixated the distractor. The results suggest that both attentional and oculomotor capture can occur in the absence of awareness, and have important implications for our understanding of the relationship between attention, eye movements, and awareness

Comparison of depth-averaged concentration and bed load flux sediment transport models of dam-break flow

This paper presents numerical simulations of dam-break flow over a movable bed. Two different mathematical models were compared: a fully coupled formulation of shallow water equations with erosion and deposition terms (a depth-averaged concentration flux model), and shallow water equations with a fully coupled Exner equation (a bed load flux model). Both models were discretized using the cell-centered finite volume method, and a second-order Godunov-type scheme was used to solve the equations. The numerical flux was calculated using a Harten, Lax, and van Leer approximate Riemann solver with the contact wave restored (HLLC). A novel slope source term treatment that considers the density change was introduced to the depth-averaged concentration flux model to obtain higher-order accuracy. A source term that accounts for the sediment flux was added to the bed load flux model to reflect the influence of sediment movement on the momentum of the water. In a one-dimensional test case, a sensitivity study on different model parameters was carried out. For the depth-averaged concentration flux model, Manning's coefficient and sediment porosity values showed an almost linear relationship with the bottom change, and for the bed load flux model, the sediment porosity was identified as the most sensitive parameter. The capabilities and limitations of both model concepts are demonstrated in a benchmark experimental test case dealing with dam-break flow over variable bed topography

Human visual search behaviour is far from ideal

Evolutionary pressures have made foraging behaviours highly efficient in many species. Eye movements during search present a useful instance of foraging behaviour in humans. We tested the efficiency of eye movements during search using homogeneous and heterogeneous arrays of line segments. The search target is visible in the periphery on the homogeneous array, but requires central vision to be detected on the heterogeneous array. For a compound search array that is heterogeneous on one side and homogeneous on the other, eye movements should be directed only to the heterogeneous side. Instead, participants made many fixations on the homogeneous side. By comparing search of compound arrays to an estimate of search performance based on uniform arrays, we isolate two contributions to search inefficiency. First, participants make superfluous fixations, sacrificing speed for a perceived (but not actual) gain in response certainty. Second, participants fixate the homogeneous side even more frequently than predicted by inefficient search of uniform arrays, suggesting they also fail to direct fixations to locations that yield the most new information

Wave propagation speeds and source term influences in single and integral porosity shallow water equations

In urban flood modeling, so-called porosity shallow water equations (PSWEs), which conceptually account for unresolved structures, e.g., buildings, are a promising approach to addressing high CPU times associated with state-of-the-art explicit numerical methods. The PSWE can be formulated with a single porosity term, referred to as the single porosity shallow water model (SP model), which accounts for both the reduced storage in the cell and the reduced conveyance, or with two porosity terms: one accounting for the reduced storage in the cell and another accounting for the reduced conveyance. The latter form is referred to as an integral or anisotropic porosity shallow water model (AP model). The aim of this study was to analyze the differences in wave propagation speeds of the SP model and the AP model and the implications of numerical model results. First, augmented Roe-type solutions were used to assess the influence of the source terms appearing in both models. It is shown that different source terms have different influences on the stability of the models. Second, four computational test cases were presented and the numerical models were compared. It is observed in the eigenvalue-based analysis as well as in the computational test cases that the models converge if the conveyance porosity in the AP model is close to the storage porosity. If the porosity values differ significantly, the AP model yields different wave propagation speeds and numerical fluxes from those of the BP model. In this study, the ratio between the conveyance and storage porosities was determined to be the most significant parameter

GeNN: a code generation framework for accelerated brain simulations

Large-scale numerical simulations of detailed brain circuit models are important for identifying hypotheses on brain functions and testing their consistency and plausibility. An ongoing challenge for simulating realistic models is, however, computational speed. In this paper, we present the GeNN (GPU-enhanced Neuronal Networks) framework, which aims to facilitate the use of graphics accelerators for computational models of large-scale neuronal networks to address this challenge. GeNN is an open source library that generates code to accelerate the execution of network simulations on NVIDIA GPUs, through a flexible and extensible interface, which does not require in-depth technical knowledge from the users. We present performance benchmarks showing that 200-fold speedup compared to a single core of a CPU can be achieved for a network of one million conductance based Hodgkin-Huxley neurons but that for other models the speedup can differ. GeNN is available for Linux, Mac OS X and Windows platforms. The source code, user manual, tutorials, Wiki, in-depth example projects and all other related information can be found on the project website http://genn-team.github.io/genn/

A Simple Algorithm of Mixing Technique of Digital Eddy Current Signals for Steam Generator Tubes

For PWR power plants, the steam generator (SG) provides a dynamic link between the reactor and the turbine generator. A steam generator typically consists of Inconel tubes anchored at intervals with stainless steel support plates. The primary coolant from the nuclear reactor circulates through these tubes. Heat, transferred to the secondary coolant by conduction through the tube wall, generating steam which is used for running the turbine