Exploration of the optimisation algorithms used in the implementation of adaptive optics in confocal and multiphoton microscopy

We report on the introduction of active optical elements into confocal and multiphoton microscopes in order to reduce the sample-induced aberration. Using a flexible membrane mirror as the active element, the beam entering the rear of the microscope objective is altered to produce the smallest point spread function once it is brought to a focus inside the sample. The conventional approach to adaptive optics, commonly used in astronomy, is to utilise a wavefront sensor to determine the required mirror shape. We have developed a technique that uses optimisation algorithms to improve the returned signal without the use of a wavefront sensor. We have investigated a number of possible optimisation methods, covering hill climbing, genetic algorithms, and more random search methods. The system has demonstrated a significant enhancement in the axial resolution of a confocal microscope when imaging at depth within a sample. We discuss the trade-offs of the various approaches adopted, comparing speed with resolution enhancement.     

Partial camera automation in an unmanned air vehicle

The present study focused on an intelligent, semiautonomous, interface for a camera operator of a simulated unmanned air vehicle (UAV). This interface used system “knowledge” concerning UAV motion in order to assist a camera operator in tracking an object moving through the landscape below. The semiautomated system compensated for the translations of the UAV relative to the earth. This compensation was accompanied by the appropriate joystick movements ensuring tactile (haptic) feedback of these system interventions. The operator had to superimpose self-initiated joystick manipulations over these system-initiated joystick motions in order to track the motion of a target (a driving truck) relative to the terrain. Tracking data showed that subjects performed substantially better with the active system. Apparently, the subjects had no difficulty in maintaining control, i.e. “following” the active stick while superimposing self-initiated control movements over the system-interventions. Furthermore, tracking performance with an active interface was clearly superior relative to the passive system. The magnitude of this effect was equal to the effect of update-frequency (2-5 Hz) of the monitor image. The benefits of update frequency enhancement and semiautomated tracking were the greatest under difficult steering conditions. Mental workload scores indicated that, for the difficult tracking-dynamics condition, both semiautomation and update frequency increase resulted in less experienced mental effort. For the easier dynamics this effect was only seen for update frequency     

Core–Shell Nanoparticle Interface and Wetting Properties

Latex colloids are among the most promising materials for broad thin film applications due to their facile surface functionalization. Yet, the effect of these colloids on chemical film and wetting properties cannot be easily evaluated. At the nanoscale, core–shell particles can deform and coalesce during thermal annealing, yielding fine‐tuned physical properties. Two different core–shell systems (soft and rigid) with identical shells but with chemically different core polymers and core sizes are investigated. The core–shell nanoparticles (NPs) are probed during thermal annealing in order to investigate their behavior as a function of nanostructure size and rigidity. X‐ray scattering allows to follow the re‐arrangement of the NPs and the structural evolution in situ during annealing. Evaluation by real‐space imaging techniques reveals a disappearance of the structural integrity and a loss of NP boundaries. The possibility to fine‐tune the wettability by tuning the core–shell NPs morphology in thin films provides a facile template methodology for repellent surfaces.     

ReliaCloud‐NS: A scalable web‐based simulation platform for evaluating the reliability of cloud computing systems

This paper discusses the implementation, architecture, and use of a graphical web‐based application called ReliaCloud‐NS that allows users to (1) evaluate the reliability of a cloud computing system (CCS) and (2) design a CCS to a specified reliability level for both public and private clouds. The software was designed with a RESTful application programming interface for performing nonsequential Monte Carlo simulations to perform reliability evaluations of a CCS. Simulation results are stored and presented to the user in the form of interactive charts and graphs from within a web browser. The software contains multiple types of CCS components, simulations, and virtual machine allocation schemes. ReliaCloud‐NS also contains a novel feature that evaluates CCS reliability across a range of varying virtual machine allocations and establishes and graphs a CCS reliability curve. This paper discusses the software architecture, the interactive web‐based interface, and the different types of simulations available in ReliaCloud‐NS and presents an overview of the results generated from a simulation.     

Cross-linking of the CAMPATH-1 antigen (CD52) mediates growth inhibition in human B- and T-lymphoma cell lines, and subsequent emergence of CD52-deficient cells

Emotional hyperthermia, circadian variations and the rise of body temperature related to exercise, have all been attributed to setpoint temperature shifts. The accepted theory holds that core temperature is regulated by corrective thermoregulatory responses opposing the core temperature deviations from the setpoint level. However, in fever and anapyrexia the thermoregulatory responses appear to be not corrective but helping, that is in the same direction as the core temperature deviation. A supplementary ad hoc hypothesis that setpoint level shifts explains why the thermoregulatory responses still could be considered "corrective" in spite of being in the same direction as the core temperature deviation. But supplementary ad hoc hypotheses immunize a theory to experimental challenges and therefore can no longer be considered a scientific theory. The present work shows that most of the arguments adduced to explain almost every biothermal phenomenon as being due to setpoint shifts cannot withstand a critical analysis.     

The Perception of Graph Properties in Graph Layouts

When looking at drawings of graphs, questions about graph density, community structures, local clustering and other graph properties may be of critical importance for analysis. While graph layout algorithms have focused on minimizing edge crossing, symmetry, and other such layout properties, there is not much known about how these algorithms relate to a user's ability to perceive graph properties for a given graph layout. In this study, we apply previously established methodologies for perceptual analysis to identify which graph drawing layout will help the user best perceive a particular graph property. We conduct a large scale (n = 588) crowdsourced experiment to investigate whether the perception of two graph properties (graph density and average local clustering coefficient) can be modeled using Weber's law. We study three graph layout algorithms from three representative classes (Force Directed ‐ FD, Circular, and Multi‐Dimensional Scaling ‐ MDS), and the results of this experiment establish the precision of judgment for these graph layouts and properties. Our findings demonstrate that the perception of graph density can be modeled with Weber's law. Furthermore, the perception of the average clustering coefficient can be modeled as an inverse of Weber's law, and the MDS layout showed a significantly different precision of judgment than the FD layout.     

Nitrogen balance in dryland agroecosystem in response to tillage,crop rotation,and cultural practice

Accounting of N inputs and outputs and N retention in the soil provides N balance that measures agroecosystem performance and environmental sustainability. Because of the complexity of measurements of some N inputs and outputs, studies on N balance in long-term experiments are scanty. We examined the effect of 8 years of tillage, crop rotation, and cultural practice on N balance based on N inputs and outputs and soil N sequestration rate under dryland cropping systems in the northern Great Plains, USA. Tillage systems were no-tillage (NT) and conventional tillage (CT) and crop rotations were continuous spring wheat (Triticum aestivum L.) (CW), spring wheat–pea (Pisum sativum L.) (W–P), spring wheat–barley (Hordeum vulgaris L.) hay–pea (W–B–P), and spring wheat–barley hay–corn (Zea mays L.)–pea (W–B–C–P). Cultural practices were traditional (conventional seed rates and plant spacing, conventional planting date, broadcast N fertilization, and reduced stubble height) and improved (variable seed rates and plant spacing, delayed planting, banded N fertilization, and increased stubble height). Total N input due to N fertilization, pea N fixation, atmospheric N deposition, crop seed N, and nonsymbiotic N fixation was greater with W–B–C–P than CW, regardless of tillage and cultural practices. Total N output due to aboveground biomass N removal and N losses due to denitrification, volatilization, plant senescence, N leaching, gaseous N (NO_x) emissions, and surface runoff were not different among treatments. Nitrogen sequestration rate at 0–20 cm from 2004 to 2011 varied from 29 kg N ha^?1 year^?1 in CT with W–P to 89 kg N ha^?1 year^?1 in NT with W–P. Nitrogen balance varied from ? 39 kg N ha^?1 year^?1 in NT with CW and the improved practice to 41 kg N ha^?1 year^?1 in CT with W–P and the traditional practice. Because of legume N fixation and increased soil N sequestration rate, diversified crop rotations reduced external N inputs and increased aboveground biomass N removal, N flow, and N balance compared with monocropping, especially in the CT system. As a result, diversified legume–nonlegume crop rotation not only reduced the cost of N fertilization by reducing N fertilization rate, but also can be productive by increasing N uptake and N surplus and environmentally sustainable by reducing N losses compared with nonlegume monocropping, regardless of cultural practices in dryland agroecosystems.     

Intersections of inequality in homeownership in Sweden

Abstract

Inequalities relating to ownership of housing have become a major issue de jour in many Western societies. This article examines how the distribution of homeownership in Sweden relates to two factors widely seen as significant to such inequalities, namely parental tenure status and place of birth. We use longitudinal registry data to examine the bearing of these two factors on individual-level tenure progression since the beginning of the 1990s for persons at different stages of their housing careers. We extend existing understandings of Swedish homeownership patterns by demonstrating that inequalities relating to place of birth and parental tenure intersect with one another in ways that substantially advantage certain subgroups while disadvantaging others, and by demonstrating that experiences of entry into homeownership have in recent years been changing in markedly different ways for these different subgroups. Overall, Swedish homeownership inequalities, far from dissipating, appear to be hardening along existing lines.     

Uptake of arsenic by New Zealand watercress (Lepidium sativum)

Watercress (Lepidium sativum) is consumed as a vegetable, especially by the indigenous community in New Zealand. An investigation was carried out on the accumulation of arsenic by watercress, following earlier reports of inordinate arsenic concentrations in some aquatic macrophytes collected from the Waikato River, North Island, New Zealand. The Waikato River and some other aquatic systems in Taupo Volcanic Zone, New Zealand have elevated arsenic concentrations due to geothermal activity. Watercress, river water and sediment samples were collected from 27 sites along the Waikato river and analysed for arsenic. Greenhouse trials with watercress grown in beakers containing added arsenic were conducted to confirm the ability of this species to accumulate arsenic. At a number of sites, the concentration of arsenic in both the water and the watercress samples exceeded the World Health Organisation (WHO) limit for drinking water (0.01 mg l(-1)) and foodstuffs (2 mg kg(-1) on a fresh weight basis). The average leaf and stem arsenic concentrations were, respectively, 29.0 and 15.9 mg kg(-1) on a fresh weight basis. Plants grown in solutions of >0.4 mg l(-1) arsenic concentration had fresh weight arsenic concentrations above the WHO limit. Despite these higher concentrations, arsenic levels in plants grown under greenhouse conditions were approximately fivefold lower than in plants growing in the Waikato River, possibly because under natural conditions, the watercress is rooted in sediment containing on average approximately 35 mg kg(-1) arsenic. It is recommended that watercress from the Waikato River, or other areas with elevated water arsenic concentrations, should not be consumed.     

Characterization of nitrogen-fixing cyanobacteria in the Brazilian Amazon floodplain

The diversity of the free-living nitrogen-fixing cyanobacterial community in the floodplain sediments along the Solimões and Amazon Rivers and some of their tributaries (Japurá, Negro and Madeira) was investigated. Five cyanobacterial genera were morphologically identified, four of which (Nostoc, Calothrix, Cylindrospermum and Fischerella) have not previously been isolated from the Brazilian Amazon floodplain. Nostoc strains were the most commonly found heterocyst-forming cyanobacteria. Five strains (N. muscorum CENA18 and CENA61, N. piscinale CENA21, Cylindrospermum sp. CENA33 and Fischerella sp. CENA19) were selected for growth measurement, ability to fix N₂ and phylogenetic analysis, based on their widespread distribution and morphological distinction. Molecular analyses employing 16S rRNA sequences indicated that some of the isolates may represent novel cyanobacterial species. Dinitrogen fixed by these strains was measured indirectly as acetylene reduction activity and ranged from 11.5 to 22.2 nmol C₂H₄ μg Chl a⁻¹ h⁻¹. These results provide evidence of widespread and importance of nitrogen-fixing cyanobacteria as a source of N inputs in the Amazonian ecosystem.