901 research outputs found
CMB Observations: improvements of the performance of correlation radiometers by signal modulation and synchronous detection
Observation of the fine structures (anisotropies, polarization, spectral
distortions) of the Cosmic Microwave Background (CMB) is hampered by
instabilities, 1/f noise and asymmetries of the radiometers used to carry on
the measurements. Addition of modulation and synchronous detection allows to
increase the overall stability and the noise rejection of the radiometers used
for CMB studies. In this paper we discuss the advantages this technique has
when we try to detect CMB polarization. The behaviour of a two channel
correlation receiver to which phase modulation and synchronous detection have
been added is examined. Practical formulae for evaluating the improvements are
presented.Comment: 18 pages, 3 figures, New Astronomy accepte
Reading visually embodied meaning from the brain: Visually grounded computational models decode visual-object mental imagery induced by written text
Embodiment theory predicts that mental imagery of object words recruits neural circuits involved in object perception. The degree of visual imagery present in routine thought and how it is encoded in the brain is largely unknown. We test whether fMRI activity patterns elicited by participants reading objects' names include embodied visual-object representations, and whether we can decode the representations using novel computational image-based semantic models. We first apply the image models in conjunction with text-based semantic models to test predictions of visual-specificity of semantic representations in different brain regions. Representational similarity analysis confirms that fMRI structure within ventral-temporal and lateral-occipital regions correlates most strongly with the image models and conversely text models correlate better with posterior-parietal/lateral-temporal/inferior-frontal regions. We use an unsupervised decoding algorithm that exploits commonalities in representational similarity structure found within both image model and brain data sets to classify embodied visual representations with high accuracy (8/10) and then extend it to exploit model combinations to robustly decode different brain regions in parallel. By capturing latent visual-semantic structure our models provide a route into analyzing neural representations derived from past perceptual experience rather than stimulus-driven brain activity. Our results also verify the benefit of combining multimodal data to model human-like semantic representations
The BLAST Survey of the Vela Molecular Cloud: Dynamical Properties of the Dense Cores in Vela-D
The Vela-D region, according to the nomenclature given by Murphy & May
(1991), of the star forming complex known as the Vela Molecular Ridge (VMR),
has been recently analyzed in details by Olmi et al. (2009), who studied the
physical properties of 141 pre- and proto-stellar cold dust cores, detected by
the ``Balloon-borne Large-Aperture Submillimeter Telescope'' (BLAST) during a
much larger (55 sq. degree) Galactic Plane survey encompassing the whole VMR.
This survey's primary goal was to identify the coldest, dense dust cores
possibly associated with the earliest phases of star formation. In this work,
the dynamical state of the Vela-D cores is analyzed. Comparison to dynamical
masses of a sub-sample of the Vela-D cores estimated from the 13CO survey of
Elia et al. (2007), is complicated by the fact that the 13CO linewidths are
likely to trace the lower density intercore material, in addition to the dense
gas associated with the compact cores observed by BLAST. In fact, the total
internal pressure of these cores, if estimated using the 13CO linewidths,
appears to be higher than the cloud ambient pressure. If this were the case,
then self-gravity and surface pressure would be insufficient to bind these
cores and an additional source of external confinement (e.g., magnetic field
pressure) would be required. However, if one attempts to scale down the 13CO
linewidths, according to the observations of high-density tracers in a small
sample of sources, then most proto-stellar cores would result effectively
gravitationally bound.Comment: This paper has 12 pages and 6 figures. Accepted for publication by
the Astrophysical Journal on July 19, 201
Machine learning based data mining for Milky Way filamentary structures reconstruction
We present an innovative method called FilExSeC (Filaments Extraction,
Selection and Classification), a data mining tool developed to investigate the
possibility to refine and optimize the shape reconstruction of filamentary
structures detected with a consolidated method based on the flux derivative
analysis, through the column-density maps computed from Herschel infrared
Galactic Plane Survey (Hi-GAL) observations of the Galactic plane. The present
methodology is based on a feature extraction module followed by a machine
learning model (Random Forest) dedicated to select features and to classify the
pixels of the input images. From tests on both simulations and real
observations the method appears reliable and robust with respect to the
variability of shape and distribution of filaments. In the cases of highly
defined filament structures, the presented method is able to bridge the gaps
among the detected fragments, thus improving their shape reconstruction. From a
preliminary "a posteriori" analysis of derived filament physical parameters,
the method appears potentially able to add a sufficient contribution to
complete and refine the filament reconstruction.Comment: Proceeding of WIRN 2015 Conference, May 20-22, Vietri sul Mare,
Salerno, Italy. Published in Smart Innovation, Systems and Technology,
Springer, ISSN 2190-3018, 9 pages, 4 figure
Onsager critical solutions of the forced Navier-Stokes equations
We answer positively to [BDL22, Question 2.4] by building new examples of solutions to the forced 3d-Navier-Stokes equations with vanishing viscosity, which exhibit anomalous dissipation and which enjoy uniform bounds in the space , for any fixed . Our construction combines ideas of [BDL22] and [CCS22]
Low Latency Protocols Investigation for Event-Driven Wireless Body Area Networks
Nowadays distributed electronic health and fitness monitoring are hot-topics in bio-engineering, however common solutions for Wireless Body Area Networks (WBANs) featuring high-density sampled data transmission still stumbles over the trade-off among data rate, application throughput, and latency. Therefore, the Bluetooth Low Energy (BLE) and the IEEE 802.15.4 protocols are here investigated, with the aim of developing an event-driven WBAN to support a threshold-crossing surface ElectroMyoGraphy (sEMG) acquisition approach. We then implemented a custom protocol to overcome their limitations and fulfil all the requirements, resulting in a transmission latency of 0.856 ms ± 1 ”s and enabling a functional operating time up to 110 h
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