Interactive feature space extension for multidimensional data projection

Projecting multi-dimensional data to a lower-dimensional visual display is a commonly used approach for identifying and analyzing patterns in data. Many dimensionality reduction techniques exist for generating visual embeddings, but it is often hard to avoid cluttered projections when the data is large in size and noisy. For many application users who are not machine learning experts, it is difficult to control the process in order to improve the “readability” of the projection and at the same time to understand their quality. In this paper, we propose a simple interactive feature transformation approach that allows the analyst to de-clutter the visualization by gradually transforming the original feature space based on existing class knowledge. By changing a single parameter, the user can easily decide the desired trade-off between structural preservation and the visual quality during the transforming process. The proposed approach integrates semi-interactive feature transformation techniques as well as a variety of quality measures to help analysts generate uncluttered projections and understand their quality

Non-ergodic effects in the Coulomb glass: specific heat

We present a numerical method for the investigation of non-ergodic effects in the Coulomb glass. For that, an almost complete set of low-energy many-particle states is obtained by a new algorithm. The dynamics of the sample is mapped to the graph formed by the relevant transitions between these states, that means by transitions with rates larger than the inverse of the duration of the measurement. The formation of isolated clusters in the graph indicates non-ergodicity. We analyze the connectivity of this graph in dependence on temperature, duration of measurement, degree of disorder, and dimensionality, studying how non-ergodicity is reflected in the specific heat.Comment: Submited Phys. Rev.

Generation of a porous scaffold with a starting composition in the CaO-SiO2-MgO-P2O5 system in a simulated physiological environment

Magnesium-based ceramics are involved in orthopedic applications such as bone scaffolds or implant coatings. They provide structural support to cells for bone ingrowth, but highly porous matrices cannot resist severe mechanical stress during implantation. In this study, the laser floating zone (LFZ) technique is used to prepare a dense crystalline material with composition in the CaO-SiO2-MgO-P2O5 system. This material, under physiological conditions, is able to generate a porous scaffold controlled by the dissolution of the MgO phase, meeting the mechanical advantages of a dense material and the biological features of a porous scaffold. FESEM (Field emission scanning electron microscopy), XRD (X-ray Diffraction), EDS (Energy Dispersive X-rays spectroscopy), and ICP ((Inductively Coupled Plasma) analysis were carried out in order to characterize the samples before and after immersion in simulated body fluid (SBF)

On the use of sniffers for spectrum occupancy measurements of Bluetooth low energy primary channels

The methods usually employed to measure channel occupancy show limitations in the context of Bluetooth Low Energy (BLE) advertisements. We propose and analyze the use of BLE sniffers as light and portable low-cost spectrum occupancy meters to be used in scenarios where real time signal analyzers are not adequate. For the measurement technique to be successful, several low-level effects must be considered. The paper argues about on-air time, receiving blind times due to processing and intra system interference, buffer saturation and frequency anchoring. Hence, a compensation procedure based on collision rate estimation is proposed. Results with the refined method show that occupancies of 40% can be measured with an overestimation error whose percentile 95% is 5 percentage points. This is reduced to 1.9 points when the occupancy is 15%. The sniffers perform in real time and are shown to correctly track short term load variations. The strategy has been successfully used to characterize occupancy in highly variable and loaded scenarios such as subway platforms and a shopping mall. Values up to 25% have been observed, which implies a relevant packet error rate. Hence, the tool can be used to make agile audits and configure the parameters that control communication redundancy in new or existing networks

Integral field spectroscopy of nitrogen overabundant blue compact dwarf galaxies

We study the spatial distribution of the physical properties and of oxygen and nitrogen abundances in three Blue Compact Dwarf Galaxiess (HS 0128+2832, HS 0837+4717 and Mrk 930) with a reported excess of N/O in order to investigate the nature of this excess and, particularly, if it is associated with Wolf-Rayet (WR) stars We have observed these BCDs by using PMAS integral field spectroscopy in the optical spectral range (3700 - 6900 {\AA}), mapping their physical-chemical properties, using both the direct method and appropriate strong-line methods. We make a statistical analysis of the resulting distributions and we compare them with the integrated properties of the galaxies. Our results indicate that outer parts of the three galaxies are placed on the "AGN-zone" of the [NII]/H{\alpha} vs. [OIII]/H{\beta} diagnostic diagram most likely due to a high N/O combined with the excitation structure in these regions. From the statistical analysis, it is assumed that a certain property can be considered as spatially homogeneous (or uniform) if a normal gaussian function fits its distribution in several regions of the galaxy. Moreover, a disagreement between the integrated properties and the mean values of the distribution usually appears when a gaussian does not fit the corresponding distribution. We find that for Mrk 930, the uniformity is found for all parameters, except for electron density and reddening. The rotation curve together with the H{\alpha} map and UV images, reveal a perturbed morphology and possible interacting processes. The N/O is found to be constant in the three studied objects at spatial scales of the order of several kpc so we conclude that the number of WR stars estimated from spectroscopy is not sufficient to pollute the ISM and to produce the observed N/O excess in these objectsComment: 17 pages, 14 figures, accepted for publication in Astronomy & Astrophysic

Quantum state of the multiverse

A third quantization formalism is applied to a simplified multiverse scenario. A well defined quantum state of the multiverse is obtained which agrees with standard boundary condition proposals. These states are found to be squeezed, and related to accelerating universes: they share similar properties to those obtained previously by Grishchuk and Siderov. We also comment on related works that have criticized the third quantization approach.Comment: 15 pages, 2 figure

Modelling diffusion of innovations in a social network

A new simple model of diffusion of innovations in a social network with upgrading costs is introduced. Agents are characterized by a single real variable, their technological level. According to local information agents decide whether to upgrade their level or not balancing their possible benefit with the upgrading cost. A critical point where technological avalanches display a power-law behavior is also found. This critical point is characterized by a macroscopic observable that turns out to optimize technological growth in the stationary state. Analytical results supporting our findings are found for the globally coupled case.Comment: 4 pages, 5 figures. Final version accepted in PR

Searching for Molecular Markers for Salt Tolerance in Rhodes Grass (\u3ci\u3eChloris gayana\u3c/i\u3e Kunth)

Rhodes grass (Chloris gayana Kunth), a C4 forage grass, is regarded as salttolerant and exhibits intra- and inter-cultivar variability for this trait. Plants of cv Boma were selected for salt tolerance at the seedling and adult stages, cloned and characterized by RAPD and AFLP amplification patterns. Both techniques were equally efficient for fingerprinting these clones. More bands were obtained by AFLP but the ratio of polymorphic bands and the proportion present only in tolerant clones were the same by both methods. These bands, along with those exclusive for sensitive clones could be useful as markers for assisted selection

Stretched exponential relaxation for growing interfaces in quenched disordered media

We study the relaxation for growing interfaces in quenched disordered media. We use a directed percolation depinning model introduced by Tang and Leschhorn for 1+1-dimensions. We define the two-time autocorrelation function of the interface height C(t',t) and its Fourier transform. These functions depend on the difference of times t-t' for long enough times, this is the steady-state regime. We find a two-step relaxation decay in this regime. The long time tail can be fitted by a stretched exponential relaxation function. The relaxation time is proportional to the characteristic distance of the clusters of pinning cells in the direction parallel to the interface and it diverges as a power law. The two-step relaxation is lost at a given wave length of the Fourier transform, which is proportional to the characteristic distance of the clusters of pinning cells in the direction perpendicular to the interface. The stretched exponential relaxation is caused by the existence of clusters of pinning cells and it is a direct consequence of the quenched noise.Comment: 4 pages and 5 figures. Submitted (5/2002) to Phys. Rev.