2,910 research outputs found
Neighbors of knots in the Gordian graph
We show that every knot is one crossing change away from a knot of
arbitrarily high bridge number and arbitrarily high bridge distance.Comment: Accepted by American Mathematical Monthly. New version incorporates
referee comment
Ostensive signals: markers of communicative relevance of gesture during demonstration to adults and children
Speakers adapt their speech and gestures in various ways for their audience. We investigated further whether they use ostensive signals (eye gaze, ostensive speech (e.g. like this, this) or a combination of both) in relation to their gestures when talking to different addressees, i.e., to another adult or a child in a multimodal demonstration task. While adults used more eye gaze towards their gestures with other adults than with children, they were more likely to use combined ostensive signals for children than for adults. Thus speakers mark the communicative relevance of their gestures with different types of ostensive signals and by taking different types of addressees into account
Analysing Magnetism Using Scanning SQUID Microscopy
Scanning superconducting quantum interference device microscopy (SSM) is a
scanning probe technique that images local magnetic flux, which allows for
mapping of magnetic fields with high field and spatial accuracy. Many studies
involving SSM have been published in the last decades, using SSM to make
qualitative statements about magnetism. However, quantitative analysis using
SSM has received less attention. In this work, we discuss several aspects of
interpreting SSM images and methods to improve quantitative analysis. First, we
analyse the spatial resolution and how it depends on several factors. Second,
we discuss the analysis of SSM scans and the information obtained from the SSM
data. Using simulations, we show how signals evolve as a function of changing
scan height, SQUID loop size, magnetization strength and orientation. We also
investigated 2-dimensional autocorrelation analysis to extract information
about the size, shape and symmetry of magnetic features. Finally, we provide an
outlook on possible future applications and improvements.Comment: 16 pages, 10 figure
Efficient solar cells by space processing
Thin films of electron beam evaporated silicon were deposited on molybdenum, tantalum, tungsten and molybdenum disilicide under ultrahigh vacuum conditions. Mass spectra from a quadrapole residual gas analyzer were used to determine the partial pressure of 13 residual gases during each processing step. Surface contamination and interdiffusion were monitored by in situ Auger electron spectrometry. The presence of phosphorus in the silicon was responsible for attaining elevated temperatures with silicide formations. Heteroepitaxial silicon growth was sensitive to the presence of oxygen during deposition, the rate and length of deposition as well as the substrate orientation
Nickel and cobalt adsorption on hydroxyapatite: a study for the de-metalation of electronic industrial wastewaters
In the present study, the Ni(II) and Co(II) adsorption efficiency and selectivity, as well adsorption mechanisms on a stoichiometric hydroxyapatite (HAP) surface have been investigated. Characterization studies (N-2 adsorption/desorption and X-ray powder diffraction (XRPD) analyses) and adsorption tests under various operative conditions provided detailed information about the use of HAP in the de-metalation of wastewaters containing Ni and Co as polluted metal species. The sorption capacity of HAP has been evaluated by static batch adsorption tests varying initial concentration of Ni(II) and Co(II) species (from ca. 0.25 to 4.3mM), contact time (from 15min to 24h), and pH (from 4 to 9) operative parameters. Proposed mechanisms of adsorption of Ni(II) and Co(II) on HAP surface are ion-exchange and surface complexation; a partial contribution of chemical precipitation from bulk solution should be considered at pH 9. In addition, adsorption isotherms of Ni(II) and Co(II) on HAP have been collected at 30 degrees C and pH 4 and modeled by employing different equations. The maximum sorption capacities have been quantified as 0.317mmolgHAP-1 (18.6mggHAP-1) and 0.382mmolgHAP-1 (22.5mggHAP-1) for Ni(II) and Co(II), respectively. Selectivity to Co and Ni in the adsorption process on HAP has also been investigated; HAP has higher affinity towards Co than Ni species (Co:Ni=2.5:1, molar ratio)
Geometric magnetism in open quantum systems
An isolated classical chaotic system, when driven by the slow change of
several parameters, responds with two reaction forces: geometric friction and
geometric magnetism. By using the theory of quantum fluctuation relations we
show that this holds true also for open quantum systems, and provide explicit
expressions for those forces in this case. This extends the concept of Berry
curvature to the realm of open quantum systems. We illustrate our findings by
calculating the geometric magnetism of a damped charged quantum harmonic
oscillator transported along a path in physical space in presence of a magnetic
field and a thermal environment. We find that in this case the geometric
magnetism is unaffected by the presence of the heat bath.Comment: 7 pages. Signs corrected. v3 Accepted in Phys. Rev.
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