42 research outputs found
Data Analysis Methods for Testing Alternative Theories of Gravity with LISA Pathfinder
In this paper we present a data analysis approach applicable to the potential
saddle-point fly-by mission extension of LISA Pathfinder (LPF). At the peak of
its sensitivity, LPF will sample the gravitational field in our Solar System
with a precision of several at frequencies
around . Such an accurate accelerometer will allow us to test
alternative theories of gravity that predict deviations from Newtonian dynamics
in the non-relativistic limit. As an example, we consider the case of the
Tensor-Vector-Scalar theory of gravity and calculate, within the
non-relativistic limit of this theory, the signals that anomalous tidal
stresses generate in LPF. We study the parameter space of these signals and
divide it into two subgroups, one related to the mission parameters and the
other to the theory parameters that are determined by the gravity model. We
investigate how the mission parameters affect the signal detectability
concluding that these parameters can be determined with the sufficient
precision from the navigation of the spacecraft and fixed during our analysis.
Further, we apply Bayesian parameter estimation and determine the accuracy to
which the gravity theory parameters may be inferred. We evaluate the portion of
parameter space that may be eliminated in case of no signal detection and
estimate the detectability of signals as a function of parameter space
location. We also perform a first investigation of non-Gaussian
"noise-glitches" that may occur in the data. The analysis we develop is
universal and may be applied to anomalous tidal stress induced signals
predicted by any theory of gravity
Integrative Neuropsychological Characteristics of Subcortical-Frontal Brain Regions as a Schizophrenia Liability Factor
Para estudiar las características de las regiones cerebrales subcórtico-frontal, se investigaron la función y la evaluación de su relación con la vulnerabilidad a la esquizofrenia en 59 pacientes y 23 controles, empleando los métodos neuropsicológicos de Luria. El análisis estableció anormalidades bilaterales de la función de las zonas lobulares prefrontal y frontal profunda en pacientes comparados con los controles. Estas anormalidades eran más predominantes en el hemisferio izquierdo. Las coeficientes de correlación punto-biserial de algunos indicadores neuropsicológicos integrativos con la vulnerabilidad a la esquizofrenia eran de 0,39 ± 0,11 y 0,28 ± 0,09, respectivamente. Los datos obtenidos llevan a la discusión de los indicadores neuropsicológicos integrativos de regiones subcortical-frontales del cerebro que se revelan como marcadores potenciales de vulnerabilidad a la esquizofrenia y confirma el papel de la asimetría estructural y funcional del cerebro en la patogénesis de la esquizofrenia.In order to study neuropsychological characteristics of subcortical-frontal brain regions function and assessment of their relation with vulnerability to schizophrenia 59 patients and 23 controls were investigated using Luria’s neuropsychological methods. The analysis established bilateral abnormalities of the function of prefrontal and profound frontal lobe zones in patients as compared with controls. These abnormalities were more predominate in the left hemisphere. Point biserial correlation coefficients of determined integrative neuropsychological indicators with liability to schizophrenia were 0.39 ± 0.11 and 0.28 ± 0.09, for the left and right brain zones respectively. The obtained data permits discussion of the integrative neuropsychological indicators of subcorticalfrontal brain regions as potential markers of liability to schizophrenia and confirms the role of structural and functional brain asymmetry in the pathogenesis of schizophrenia
Data series subtraction with unknown and unmodeled background noise
LISA Pathfinder (LPF), ESA's precursor mission to a gravitational wave
observatory, will measure the degree to which two test-masses can be put into
free-fall, aiming to demonstrate a residual relative acceleration with a power
spectral density (PSD) below 30 fm/s/Hz around 1 mHz. In LPF data
analysis, the measured relative acceleration data series must be fit to other
various measured time series data. This fitting is required in different
experiments, from system identification of the test mass and satellite dynamics
to the subtraction of noise contributions from measured known disturbances. In
all cases, the background noise, described by the PSD of the fit residuals, is
expected to be coloured, requiring that we perform such fits in the frequency
domain. This PSD is unknown {\it a priori}, and a high accuracy estimate of
this residual acceleration noise is an essential output of our analysis. In
this paper we present a fitting method based on Bayesian parameter estimation
with an unknown frequency-dependent background noise. The method uses noise
marginalisation in connection with averaged Welch's periodograms to achieve
unbiased parameter estimation, together with a consistent, non-parametric
estimate of the residual PSD. Additionally, we find that the method is
equivalent to some implementations of iteratively re-weighted least-squares
fitting. We have tested the method both on simulated data of known PSD, and to
analyze differential acceleration from several experiments with the LISA
Pathfinder end-to-end mission simulator.Comment: To appear Phys. Rev. D90 August 201
Unveiling the gravitational universe at mu-Hz frequencies
Funding Information: Open access funding provided by Università degli Studi di Milano - Bicocca within the CRUI-CARE Agreement. Publisher Copyright: © 2021, The Author(s).We propose a space-based interferometer surveying the gravitational wave (GW) sky in the milli-Hz to mu-Hz frequency range. By the 2040s, the mu-Hz frequency band, bracketed in between the Laser Interferometer Space Antenna (LISA) and pulsar timing arrays, will constitute the largest gap in the coverage of the astrophysically relevant GW spectrum. Yet many outstanding questions related to astrophysics and cosmology are best answered by GW observations in this band. We show that a mu-Hz GW detector will be a truly overarching observatory for the scientific community at large, greatly extending the potential of LISA. Conceived to detect massive black hole binaries from their early inspiral with high signal-to-noise ratio, and low-frequency stellar binaries in the Galaxy, this instrument will be a cornerstone for multimessenger astronomy from the solar neighbourhood to the high-redshift Universe.Peer reviewe
Radiation pressure calibration and test mass reflectivities for LISA Pathfinder
This paper describes a series of experiments which were carried out during the main operations of LISA Pathfinder. These experiments were performed by modulating the power of the measurement and reference beams. In one series of experiments the beams were sequentially switched on and off. In the other series of experiments the powers of the beams were modulated within 0.1% and 1% of the constant power. These experiments use recordings of the total power measured on the photodiodes to infer the properties of the Optical Metrology System (OMS), such as reflectivities of the test masses and change of the photodiode efficiencies with time. In the first case the powers are back propagated from the different photodiodes to the same place on the optical bench to express the unknown quantities in the measurement with the complimentary photodiode measurements. They are combined in the way that the only unknown left is the test mass reflectivities. The second experiment compared two estimates of the force applied to the test masses due to the radiation pressure that appears because of the beam modulations. One estimate of the force is inferred from the measurements of the powers on the photodiodes and propagation of this measurement to the test masses. The other estimation of the force is done by calculating it from the change in the main scientific output of the instrument – differential displacement of the two test masses
Laser Interferometer Space Antenna
Following the selection of The Gravitational Universe by ESA, and the
successful flight of LISA Pathfinder, the LISA Consortium now proposes a 4 year
mission in response to ESA's call for missions for L3. The observatory will be
based on three arms with six active laser links, between three identical
spacecraft in a triangular formation separated by 2.5 million km.
LISA is an all-sky monitor and will offer a wide view of a dynamic cosmos
using Gravitational Waves as new and unique messengers to unveil The
Gravitational Universe. It provides the closest ever view of the infant
Universe at TeV energy scales, has known sources in the form of verification
binaries in the Milky Way, and can probe the entire Universe, from its smallest
scales near the horizons of black holes, all the way to cosmological scales.
The LISA mission will scan the entire sky as it follows behind the Earth in its
orbit, obtaining both polarisations of the Gravitational Waves simultaneously,
and will measure source parameters with astrophysically relevant sensitivity in
a band from below Hz to above Hz.Comment: Submitted to ESA on January 13th in response to the call for missions
for the L3 slot in the Cosmic Vision Programm
A new look at an old problem: the category of “syndrome” in psychology
The paper deals with a complex of issues relating to the current state and use of the category of “syndrome”, which until recently has been inclusive within the field of professional medical use and clinical psychology. However, since late 20th century, this category has been more and more often used when describing the specific manifestations of human psyche in the particular circumstances of life and activity with the absence of disease symptoms and presented a huge list of so-called “psychological syndromes” of the norm. In this connection, there arise a number of issues concerning the relations of new approaches to understanding the category of “syndrome” with past performances, and also research methodology, which determines task setting, the unit of analysis of human psyche and psychological syndrome-making determinants. The authors assume the answer to these questions lie in the methodology by L.S.Vygotsky and further syndrome analysis method by A.R. Luria. The paper provides a brief history of the notion of “syndrome” and its transition from medical study to psychology with the developed meaning based on the structure of higher mental functions in the neuropsychological paradigm. The basic structural components of the syndrome in system-dynamic relationship are discussed. Special attention is paid to the problem of “factor” as a common syndrome-making state which integrates symptoms into hierarchically organized circuit. Various aspects of the categorization are discussed, i.e. whether it belongs to the norm or pathology. In the context of the syndrome approach development prospects, new issues of polycausativity syndrome appear in relation to the classical paradigm, with compensatory symptoms, the need for statistical data verification, the role of individual supervision and others to be further included into the paradigm. The main current approaches of studying different syndromes using the potential of the Russian methodology of syndrome analysis, the basic principles of postnonclassical model of scientific rationality are considered