8,120 research outputs found
Cognitive demands of face monitoring: Evidence for visuospatial overload
No full textYoung children perform difficult communication tasks better face to face than when they cannot see one another (e.g., Doherty-Sneddon & Kent, 1996). However, in recent studies, it was found that children aged 6 and 10 years, describing abstract shapes, showed evidence of face-to-face interference rather than facilitation. For some communication tasks, access to visual signals (such as facial expression and eye gaze) may hinder rather than help children’s communication. In new research we have pursued this interference effect. Five studies are described with adults and 10- and 6-year-old participants. It was found that looking at a face interfered with children’s abilities to listen to descriptions of abstract shapes. Children also performed visuospatial memory tasks worse when they looked at someone’s face prior to responding than when they looked at a visuospatial pattern or at the floor. It was concluded that performance on certain tasks was hindered by monitoring another person’s face. It is suggested that processing of visual communication signals shares certain processing resources with the processing of other visuospatial information
Deep anisotropic dry etching of silicon microstructures by high-density plasmas
No full textThis thesis deals with the dry etching of deep anisotropic microstructures in monocrystalline silicon by high-density plasmas. High aspect ratio trenches are necessary in the fabrication of sensitive inertial devices such as accellerometers and gyroscopes. The etching of silicon in fluorine-based plasmas is isotropic. To obtain anisotropy the addition of sidewall passivation is necessary. This is achieved with both oxygen passivation at low temperatures and fluorocarbon passivation at room temperature. A quantitative approach was pursued to explain the etching mechanism. The etch results were analysed using the measured plasma species fluxes and the surface composition. Moreover, the transport of the plasma species in narrow anisotropic structures is a fundamental factor determining the etch rate and the profile evolution. The experimental methods such as the etching equipment, plasma diagnostics, surface analysis and sample preparation are described in chapter 2. Three etching processes were investigated: the cryogenic etching process with oxygen passivation at low temperatures, the Bosch process with fluorocarbon passivation at room temperature and the novel triple pulse process that was developed in our laboratory. The polymer deposition mechanism and the characteristic role of the ions are also explained. The cryogenic etching process is discussed in chapter 3. Fluorine radicals, oxygen radicals and ion bombardment are responsible for the three main sub-processes, that is, etching, sidewall passivation and depassivation of the trench bottom, respectively. Etching experiments with an extremely low ion-to-radical flux ratio were used to reveal the etching mechanism. Crystal orientation dependent etching leading to Si(111) crystal facets is observed in a surface kinetics controlled regime. By varying the plasma conditions it is possible to adjust the etching mechanism from fluorine-limited to ion-limited. Controlled etching is obtained because the etching is tuned from aspect ratio dependent in the fluorine-limited domain to aspect ratio independent in the ion-limited domain. The transport of radicals in high aspect ratio trenches is an important limiting factor and was investigated with special structures. The etch results are described by an analytic model that is based on the surface site balance of fluorine and oxygen radicals. The results are further explained with a Monte Carlo simulation model. The Bosch process is clarified in chapter 4. The anisotropy of the etched structures is controlled by balancing the etching and passivation pulse. However, the maximal obtainable aspect ratio is limited by convergence of the trench sidewalls due to excessive passivation. The maximal obtainable aspect ratio increases if the ion-to-radical flux ratio increases. The transport of ions is an important limiting factor in the depassivation of the bottom of the trench. Divergence of the ion beam leads to a reduction of the ion flux, so that the fluorocarbon passivation is insufficiently removed near the base of the sidewalls. The average ion angle was measured and correlated to the maximal obtainable aspect ratio. The Bosch process was improved at the depassivation side with the triple pulse process and at the passivation side with preferential sidewall deposition. The triple pulse process that is described in chapter 5 has the aim to improve the depassivation in deep trenches. The three main sub-processes are decoupled using a separate depassivation pulse directly after the etching and passivation pulses. The fluorocarbon passivation is efficiently removed with low-pressure, high-density, oxygen-based plasmas. The investigated plasma chemistries include O2, CO2 and SO2. The triple pulse process leads to better profile control with a straight trench bottom. However, the maximal obtainable aspect ratio is comparable to the Bosch process because a larger etch depth and a small lateral etch cancel out. The polymer deposition mechanism is treated in chapter 6 with the aim to understand the fluorocarbon passivation in deep trenches. The deposition on plane surfaces and on special structures was investigated to distinguish between the radical-induced and ion-enhanced components. A simple analytical model, which explains the main deposition characteristics, was developed. Preferential sidewall deposition is obtained for higher ion fluxes and higher bias voltages where sputtering plays an important role. In this case no fluorocarbon passivation has to be removed from the bottom of the trench. The trench profile was optimised in the Bosch process by tuning the bias voltage during etching and passivation independently. It resulted in perfectly anisotropic trenches but the maximal obtainable aspect ratio was still limited by a small lateral etch. The characteristic role of the ions in the etching mechanism is explained in chapter 7. Ion-induced etching of both SiC in a SF6-O2 plasma and Si in a Cl2 plasma were investigated. The impact of the ions on the profile evolution can be examined more explicitly because spontaneous chemical reactions are absent for these plasma-material systems. The etching mechanism varies from fluorine-limited to ion-limited depending on the radical-to-ion flux ratio. Microtrenches are observed for an ion-limited etching mechanism. Fluorine-limited SiC etching is aspect ratio dependent in contrast to ion-limited SiC etching, which is aspect ratio independent. The etching of high aspect ratio SiC structures is limited by the positive sidewall taper. This is presumably caused by insufficient removal of the thin fluorocarbon layer on the surface. Si etching in a Cl2 plasma is always aspect ratio independent in contrast to SiC etching because of the low reaction probability. The conclusions and recommendations of this thesis are given in chapter 8.Applied Science
Split-domain calibration of an ecosystem model using satellite ocean colour data
No full textThe application of satellite ocean colour data to the calibration of plankton
ecosystem models for large geographic domains, over which their ideal parameters cannot be assumed to be invariant, is investigated. A method is presented for seeking the number and geographic scope of parameter sets which allows the best fit to validation data to be achieved. These are independent data not used in the parameter estimation process. The goodness-of-fit of the optimally calibrated model to the validation data is an objective measure of merit for the model, together with its external forcing data. Importantly, this is a statistic which can be used for comparative evaluation of different models. The method makes use of observations from multiple locations, referred to as stations, distributed across the geographic domain. It relies on a technique for finding groups of stations which can be aggregated for parameter estimation purposes with minimal increase in the resulting misfit between model and observations.The results of testing this split-domain calibration method for a simple zero dimensional model, using observations from 30 stations in the North Atlantic, are presented. The stations are divided into separate calibration and validation sets.
One year of ocean colour data from each station were used in conjunction with a
climatological estimate of the station’s annual nitrate maximum. The results
demonstrate the practical utility of the method and imply that an optimal fit of the model to the validation data would be given by two parameter sets. The corresponding division of the North Atlantic domain into two provinces allows a misfit-based cost to be achieved which is 25% lower than that for the single parameter set obtained using all of the calibration stations. In general, parameters are poorly constrained, contributing to a high degree of uncertainty in model output for unobserved variables. This suggests that limited progress towards a definitive model calibration can be made without including other types of observations
Parameterizing the microbial loop: an experiment in reducing model complexity
No full textThe structure of the plankton food web in the upper mixed layer has important implications for the export of biogenic material from the euphotic zone. While the action of the microbial loop causes material to be recycled near the surface, activity of the larger zooplankton leads to a significant downward flux of material. The balance between these pathways must be properly represented in climate models to predict carbon export. However, the number of biogeochemical compartments available to represent the food web is limited by the need to couple biogeochemical models with general circulation models. A structurally simple model is therefore sought, with a number of free parameters, which can be constrained by available observations to produce reliable estimates of export.A step towards addressing this aim is described: an attempt is made to emulate the behavior of an 11 compartment model with an explicit microbial loop, using a 4 compartment model. The latter, incorporating a basic microbial loop parameterization, is derived directly from the 'true' model. The results are compared with equivalent results for a 4 compartment model with no representation of the microbial loop. These non-identical twin experiments suggest that export estimates from 4 compartment models are prone to serious biases in regions where the action of the microbial loop is significant. The basic parameterization shows some promise in addressing the problem but a more sophisticated parameterization would be needed to produce reliable estimates. Some recommendations are made for future research
Assessment of Models for Near Wall Behavior and Swirling Flows in Nuclear Reactor Sub-system Simulations
No full textAccurate simulation of turbulence remains one of the most challenging problems in nuclear reactor analysis and design. Due to limitations in computing resources, Reynolds averaged Navier Stokes models (RANS) continue to play an important role in reactor simulations. The Consortium for advanced simulations of light water reactors (CASL) is a Department of Energy technology hub that is investing in research and developmentof a state-of-the-art computational fluid dynamics capabilityto meet the challenges of turbulent simulation of nuclear reactors. In this presentation, we assess several RANS eddy viscosity models appropriate for single-phase incompressible turbulent flows. Specifically, we compare the single equation Splalart-Allmaras to several variations of the model. The assessment takes into consideration elements of full system reactor cores such as complex geometries, heterogeneous meshes, swirling flow, near wall flow behavior, heat transfer and robustness issues. The goal of this strategically oriented assessment is to provide an accurate and robust turbulent simulation capability for the CASL community. Metrics of performance will be constructed by comparing different models on a strategically chosen set of problems that represent reactor core sub-systems
O zarubežnoj dejatel'nosti professora M.A. Kumaxova
No full textOn professor M.A. Kumakhov's work and research abroad (in Russian)
Professor Mukhadin A. Kumakhov and the author collaborated in the area of Northwest Caucasian languages under a period from 1991 to 2008. The fruitful collaboration at Lund and Malmö universities resulted in three joint monographs and a number of articles, which is outlined in the article. Mukhadin A. Kumakhov became Honorary Doctor of the Philosophical Faculty of Lund University in 1998
Bringing clouds into our lab!: The influence of turbulence on early stage rain droplets
No full textWe are investigating a droplet-laden flow in an air-filled turbulence chamber, forced by speaker-driven air jets. The speakers are running in a random manner; yet they allow us to control and define the statistics of the turbulence. We study the motion of droplets with tunable size in a turbulent flow, mimicking the early stages of raindrop formation. 3D Particle Tracking Velocimetry (PTV) is chosen as the experimental method to track the droplets and collect data for statistical analysis. Thereby it is possible to study the spatial distribution of the droplets in turbulence using the so-called Radial Distribution Function (RDF), a statistical measure to quantify the clustering of particles. Additionally, this technique allows us to measure velocity statistics of the droplets and the influence of the turbulence on droplet trajectories, both individually and collectively. In this contribution, we will present velocity statistics of the droplets and quantify their clustering using the RDF for different turbulence conditions
The Story about the constructed SARS COV-2 Virus - A Review of three Research Groups
No full textAbstract
A literature research on synthetic recombinant SARS Coronavirus was made to answer two questions. Is the SARS CoV-2 virus designed in a laboratory? And why has the SARS CoV-2 such a high mutation rate? A total of 12 research articles, 2 reviews and 10 experimental studies were attributed to three Research Groups, the Wadsworth Center New York, the Vanderbilt Medical Center, and the Chapel Hill North Carolina. The research papers were published between 1991 and 2014. All 12 research papers reported the successful construction of recombinant SARS Coronaviruses based on RNA reverse genetic and molecular techniques. The Research group from the Medical Center at Vanderbilt University proved how an engineered SARS Coronavirus with an impaired Exonuclease resulted in a progeny virus with high mutation rate. Furthermore, the review showed that a zoonotic-human transmission was just possible with specific genetic manipulations at the SARS CoV virus genome through selection of virus species for recombination, and targeted manipulation at non-structural virus domains. But importantly, the studies showed that a SARS Coronavirus cross-species infection such as between zoonotic and humans or between different animal species without the exchange of the virus spike protein domain with the host-specific receptor-binding domain (RBD) and additional point mutations was not possible. Therefore, the SARS CoV-2 was deliberately constructed to overcome the receptor limiting factor for animal-human infection. Interestingly, the review revealed that the study purpose of constructed recombinant SARS CoV changed from the scientific research point of view to vaccine production and development. Competing interests for all reviewed studies by grants from private investors such as the Gates Foundation and vaccine production companies were part of the discussion. Keywords: SARS CoV-2, Covid19, Spike protein, gene sequencing, Vanderbilt University, University North Carolina, Wadsworth Research Center, New York Health Department, Coronavirus, Bill & Melinda Gates Foundation, WHO, Pfizer, Merck, Novartis, AlphaVaxThe author declares no competing interests.
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The force of law as a social problem
No full textIn this paper, the author aims to respond to the urgings in the book “The Force of Law” by Frederick Schauer breaking from the paradigm of analytical jurisprudence, insofar as the University of Virginia philosopher states having found sociological bases for his own logical/reconstructive architecture. The author, on the one hand, intend to develop a critique of Schauer’s approach that is not merely theoretical, but sociological as well; on another hand, Hart’s thesis on force in law—strongly criticized by contemporary analytical philosophers—is not therefore rebuffed by sociological analysis but somehow finds confirmation. In a nutshell, whether the use of force is sociologically necessary to control isolated resistance to the rules shared by the majority, or to reinforce a law, that aims to trigger necessary social change, but such a strong limitation of human freedom must be justified; and this legitimacy can only derive from the need for Justic
Home and family in the novels 'The White Guard' by M.A. Bulgakov and 'The Suicide' by M.A. Aldanov: A look at the revolution from the 'inside' and the 'outside'
No full textThe sociocultural content of the concept of family hearth under the conditions of the revolutionary events of 1917 described in the novels “The Suicide” (‘Samoubiistvo’) by M.A. Aldanov and “The White Guard” (‘Belaya gvardiya’) by M.A. Bulgakov was revealed.
The relevance of the study is determined by the fact that the concepts of home and family are the basic components of the sociocultural consciousness of any society.
The study was performed with the aim of identifying key motifs in the description of home, as well as similarities and differences in the linguistic representation of this concept when describing two periods in the history of Russia (during the pre-revolutionary and revolutionary times) from the position of the author as an eyewitness to the events and the author as an emigrant.
The following conclusions were made: in the descriptions of home of the pre-revolutionary Russia in the novels “The White Guard” by M.A. Bulgakov and “The Suicide” by M.A. Aldanov, the motifs of the well-being, stability, and continuity of generations are emphasized. In the episodes depicting the revolutionary events, the linguistic representation of home and family changes considerably: the motifs of doom, regret about the lost, surrealism, and tenuous imaginings become evident.
The results obtained are important for linguistic analysis of some passages of the text needed for the adequate perception of the novels “The White Guard” by M.A. Bulgakov and “The Suicide” by M.A. Aldanov
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