Utility and lower limits of frequency detection in surface electrode stimulation for somatosensory brain-computer interface in humans

Objective: Stimulation of the primary somatosensory cortex (S1) has been successful in evoking artificial somatosensation in both humans and animals, but much is unknown about the optimal stimulation parameters needed to generate robust percepts of somatosensation. In this study, the authors investigated frequency as an adjustable stimulation parameter for artificial somatosensation in a closed-loop brain-computer interface (BCI) system. Methods: Three epilepsy patients with subdural mini-electrocorticography grids over the hand area of S1 were asked to compare the percepts elicited with different stimulation frequencies. Amplitude, pulse width, and duration were held constant across all trials. In each trial, subjects experienced 2 stimuli and reported which they thought was given at a higher stimulation frequency. Two paradigms were used: first, 50 versus 100 Hz to establish the utility of comparing frequencies, and then 2, 5, 10, 20, 50, or 100 Hz were pseudorandomly compared. Results: As the magnitude of the stimulation frequency was increased, subjects described percepts that were “more intense” or “faster.” Cumulatively, the participants achieved 98.0% accuracy when comparing stimulation at 50 and 100 Hz. In the second paradigm, the corresponding overall accuracy was 73.3%. If both tested frequencies were less than or equal to 10 Hz, accuracy was 41.7% and increased to 79.4% when one frequency was greater than 10 Hz (p = 0.01). When both stimulation frequencies were 20 Hz or less, accuracy was 40.7% compared with 91.7% when one frequency was greater than 20 Hz (p < 0.001). Accuracy was 85% in trials in which 50 Hz was the higher stimulation frequency. Therefore, the lower limit of detection occurred at 20 Hz, and accuracy decreased significantly when lower frequencies were tested. In trials testing 10 Hz versus 20 Hz, accuracy was 16.7% compared with 85.7% in trials testing 20 Hz versus 50 Hz (p < 0.05). Accuracy was greater than chance at frequency differences greater than or equal to 30 Hz. Conclusions: Frequencies greater than 20 Hz may be used as an adjustable parameter to elicit distinguishable percepts. These findings may be useful in informing the settings and the degrees of freedom achievable in future BCI systems

Wide-Field Chandra X-Ray Observations of AGN in Abell 85 & Abell 754

To better understand the mechanism or mechanisms that lead to AGN activity today, we measure the X-ray AGN fraction in a new sample of nearby clusters and examine how it varies with galaxy properties, projected cluster-centric radius, and cluster velocity dispersion. We present new wide-field Chandra X-ray Observatory observations of Abell 85, Abell 754 and the background cluster Abell 89B out to their virial radii. Out of seventeen X-ray sources associated with galaxies in these clusters, we classify seven as X-ray AGN with L_{X,B} > 10^{41} erg/s. Only two of these would be classified as AGN based on their optical spectra. We combine these observations with archival data to create a sample of X-ray AGN from six z < 0.08 clusters and find that 3.4+1.1/-0.8% of M_R 10^{41} erg/s. We find that more X-ray AGN are detected in more luminous galaxies and attribute this to larger spheriods in more luminous galaxies and increased sensitivity to lower Eddington-rate accretion from black holes in those spheroids. At a given X-ray luminosity limit, more massive black holes can be accreting less efficiently, yet still be detected. If interactions between galaxies are the principal drivers of AGN activity, then the AGN fraction should be higher in lower velocity dispersion clusters and the outskirts of clusters. However, the tendency of the most massive and early-type galaxies to lie in the centers of the richest clusters could dilute such trends. While we find no variation in the AGN fraction with projected cluster-centric radius, we do find that the AGN fraction increases significantly from 2.6+1.0/-0.8% in rich clusters to 10.0+6.2/-4.3% in those with lower velocity dispersions.Comment: Accepted by Astrophysical Journal, 17 pages using emulateapj.cls, 10 B & W Figures (degraded): Full resolution paper available at http://www.astronomy.ohio-state.edu/~sivakoff/AGN/XAGN_A85_A754.pd

Mitigación de ataques de denegación de servicio distribuidos en la nube

Los costos de los servicios de mitigación de ataques de DDoS generalmente resultan difíciles de afrontar para pequeñas y medianas organizaciones. Debido a esto, se propone el desarrollo de una plataforma utilizando estándares abiertos y software libre para proveer un servicio propio de mitigación DDoS y que distintos tipos de organizaciones, de manera individual o coordinada, puedan utilizarlo. Esta plataforma se conforma de diversas componentes, entre las que sobresalen los nodos de limpieza de tráfico distribuidos administrables desde una única interfaz web.Facultad de Informátic

SuSAv2 Model for Inelastic Neutrino-nucleus Scattering

The susperscaling model SuSAv2, already available for charged-current neutrino-nucleus cross sections in the quasielastic region, is extended to the full inelastic regime. In the model the resonance production and deep inelastic reactions are described through the extension to the neutrino sector of the SuSAv2 inelastic model developed for (e, e′) reactions, which combines phenomenological structure functions with a nuclear scaling function. This work also compares two different descriptions of the Δ resonance region, one based on a global scaling function for the full inelastic spectrum and the other on a semiphenomenological Δ scaling function extracted from (e, e′) data for this specific region and updated with respect to previous work. The results of the model are tested against (e, e′) data on C12, O16, Ca40, and Ar40 and applied to the study of the charged current inclusive neutrino cross-section on C12 and Ar40 measured by the T2K, MicroBooNE, ArgoNEUT, and MINERvA experiments, thus covering several kinematical regions.Ministerio de Ciencia e Innovación PID2020–114687 GB-I00Ministerio de Ciencia, Innovación y Universidades FIS2017-88410-Junta de Andalucía FQM160, SOMM17/6105/UGR, USE-21618-KUniversity of Tokyo FY2020, FY2021European Union 83948

HST Photometry and Keck Spectroscopy of the Rich Cluster MS1054-03: Morphologies, Butcher-Oemler Effect and the Color-Magnitude Relation at z=0.83

We present a study of 81 I selected, spectroscopically-confirmed members of the X-ray cluster MS1054-03 at z=0.83. Redshifts and spectral types were determined from Keck spectroscopy. Morphologies and accurate colors were determined from a large mosaic of HST WFPC2 images in F606W and F814W. Early-type galaxies constitute only 44% of this galaxy population. Thirty-nine percent are spiral galaxies, and 17% are mergers. The early-type galaxies follow a tight and well-defined color-magnitude relation, with the exception of a few outliers. The observed scatter is 0.029 +- 0.005 magnitudes in restframe U-B. Most of the mergers lie close to the CM relation defined by the early-type galaxies. They are bluer by only 0.07 +- 0.02 magnitudes, and the scatter in their colors is 0.07 +- 0.04 magnitudes. Spiral galaxies in MS1054-03 exhibit a large range in their colors. The bluest spiral galaxies are 0.7 magnitudes bluer than the early-type galaxies, but the majority is within +- 0.2 magnitudes of the early-type galaxy sequence. The red colors of the mergers and the majority of the spiral galaxies are reflected in the fairly low Butcher-Oemler blue fraction of MS1054-03: f_B=0.22 +- 0.05. The slope and scatter of the CM relation of early-type galaxies are roughly constant with redshift, confirming previous studies that were based on ground-based color measurements and very limited membership information. However, the scatter in the combined sample of early-type galaxies and mergers is twice as high as the scatter of the early-type galaxies alone. This is a direct demonstration of the ``progenitor bias'': high redshift early-type galaxies seem to form a homogeneous, old population because the progenitors of the youngest present-day early-type galaxies are not included in the sample.Comment: Accepted for publication in the ApJ. At http://astro.caltech.edu/~pgd/cm1054/ color figures can be obtaine

Semi-inclusive charged-current neutrino-nucleus reactions: Analysis of data in the Relativistic Plane-Wave Impulse Approximation

Semi-inclusive neutrino-nucleus cross sections within the plane-wave impulse approximation (PWIA) for three nuclear models: relativistic Fermi gas (RFG), independent-particle shell model (IPSM) and natural orbitals shell model (NO) are compared with the available CC0π measurements from the T2K, MINERνA and MicroBooNE collaborations where a muon and at least one proton were detected in the final state. Results are presented as a function of the momenta and angles of the final particles, as well as in terms of the imbalances between proton and muon kinematics. The analysis reveals that contributions beyond PWIA are crucial to explain the experimental measurements and that the study of correlations between final-state proton and muon kinematics can provide valuable information on relevant nuclear effects such as initial state dynamics and final state interactions.Ministerio de Ciencia, Innovación y Universidades FIS2017-88410-PJunta de Andalucía PID2020-114687GB-10

Superscaling in the resonance region for neutrino-nucleus scattering: The SuSAv2 dynamical coupled-channels model

In this work, the SuSAv2 and dynamical coupled-channels (DCC) models have been combined and tested in the inelastic regime for electron and neutrino reactions on nuclei. The DCC model, an approach to study baryon resonances through electron and neutrino induced meson production reactions, has been implemented for the first time in the SuSAv2-inelastic model to analyze the resonance region. Within this framework, we also present a novel description about other inelasticities in the resonance region (SoftDIS). The outcomes of these approaches are firstly benchmarked against (e, e′) data on 12C. The description is thus extended to the study of neutrino-nucleus inclusive cross sections on 12C and 40Ar and compared with data from the T2K, MicroBooNE, ArgoNEUT, and MINERvA experiments, thus covering a wide kinematical range.Ministerio de Ciencia, Innovación y Universidades (MICINN). España PID2020–114687 GB-100European Commission (EC). Fondo Europeo de Desarrollo Regional (FEDER) PID2020–114687 GB-100Junta de Andalucía. FQM160, SOMM17/6105/UGR/UGR, P20-01247University of Tokyo. 2022i-J-001, 2023i-J-001INFN. Project Iniziativa Specifica NucSysUniversity of Turin.BARM-RILO-20Universidad de Sevilla. PID2020–114687 GB-10

Mean-field and two-body nuclear effects in inclusive electron scattering on argon, carbon, and titanium: The superscaling approach

We compare the predictions of the superscaling approach (SuSAv2) model including two-particle two-hole meson-exchange currents with the recent JLab data for inclusive electron scattering on three different targets (C, Ar, and Ti). The agreement is very good over the full energy spectrum, with some discrepancy seen only in the deep inelastic region. The 2p2h response, peaked in the dip region between the quasielastic and Δ-resonance peak, is essential to reproduce the data. We also analyze the kF (Fermi momentum) dependence of the data in terms of scaling of the second kind, showing that the 2p2h response scales very differently from the quasielastic one, in full accord with what is predicted by the model. The results represent a valuable test of the applicability of the model to neutrino scattering processes on different nuclei.Spanish Ministerio de Economia y Competitividad y ERDF (European Regional Development Fund) FIS2017-88410-PJunta de Andalucía FQM160U.S. Department of Energy United States Department of Energy (DOE), DE-FC0294ER4081

Asymmetric relativistic Fermi gas model for quasielastic lepton-nucleus scattering

We develop an asymmetric relativistic Fermi gas model for the study of the electroweak nuclear response in the quasielastic region. The model takes into account the differences between neutron and proton densities in asymmetric (N>Z) nuclei, as well as differences in the neutron and proton separation energies. We present numerical results for both neutral and charged-current processes, focusing on nuclei of interest for ongoing and future neutrino oscillation experiments. We point out some important differences with respect to the commonly employed symmetric Fermi gas model.University of Turin BARM-RILO-17Junta de Andalucía FQM160Spanish Ministerio de Economía y Competitividad and ERDF (European Regional Development Fund) FIS2014-53448-C2-1, FIS2017-88410-