1,945 research outputs found
Future constraints on halo thermodynamics from combined Sunyaev-Zel'dovich measurements
The improving sensitivity of measurements of the kinetic Sunyaev-Zel'dovich
(SZ) effect opens a new window into the thermodynamic properties of the baryons
in halos. We propose a methodology to constrain these thermodynamic properties
by combining the kinetic SZ, which is an unbiased probe of the free electron
density, and the thermal SZ, which probes their thermal pressure. We forecast
that our method constrains the average thermodynamic processes that govern the
energetics of galaxy evolution like energetic feedback across all redshift
ranges where viable halos sample are available. Current Stage-3 cosmic
microwave background (CMB) experiments like AdvACT and SPT-3G can measure the
kSZ and tSZ to greater than 100 if combined with a DESI-like
spectroscopic survey. Such measurements translate into percent-level
constraints on the baryonic density and pressure profiles and on the feedback
and non-thermal pressure support parameters for a given ICM model. This in turn
will provide critical thermodynamic tests for sub-grid models of feedback in
cosmological simulations of galaxy formation. The high fidelity measurements
promised by the next generation CMB experiment, CMB-S4, allow one to further
sub-divide these constraints beyond redshift into other classifications, like
stellar mass or galaxy type.Comment: 11 pages, 3 figures, Accepted to JCA
Functional and neural mechanisms of human fear conditioning: studies in healthy and brain-damaged individuals
Fear conditioning represents the learning process by which a stimulus, after repeated pairing with an aversive event, comes to evoke fear and becomes intrinsically aversive. This learning is essential to organisms throughout the animal kingdom and represents one the most successful laboratory paradigm to reveal the psychological processes that govern the expression of emotional memory and explore its neurobiological underpinnings.
Although a large amount of research has been conducted on the behavioural or neural correlates of fear conditioning, some key questions remain unanswered. Accordingly, this thesis aims to respond to some unsolved theoretic and methodological issues, thus furthering our understanding of the neurofunctional basis of human fear conditioning both in healthy and brain-damaged individuals. Specifically, in this thesis, behavioural, psychophysiological, lesion and non-invasive brain stimulation studies were reported. Study 1 examined the influence of normal aging on context-dependent recall of extinction of fear conditioned stimulus. Study 2 aimed to determine the causal role of the ventromedial PFC (vmPFC) in the acquisition of fear conditioning by systematically test the effect of bilateral vmPFC brain-lesion. Study 3 aimed to interfere with the reconsolidation process of fear memory by the means of non-invasive brain stimulation (i.e. TMS) disrupting PFC neural activity. Finally, Study 4 aimed to investigate whether the parasympathetic – vagal – modulation of heart rate might reflect the anticipation of fearful, as compared to neutral, events during classical fear conditioning paradigm.
Evidence reported in this PhD thesis might therefore provide key insights and deeper understanding of critical issues concerning the neurofunctional mechanisms underlying the acquisition, the extinction and the reconsolidation of fear memories in humans
The Kinematic Sunyaev-Zel'dovich Effect with Projected Fields II: prospects, challenges, and comparison with simulations
The kinematic Sunyaev-Zel'dovich (kSZ) signal is a powerful probe of the
cosmic baryon distribution. The kSZ signal is proportional to the integrated
free electron momentum rather than the electron pressure (which sources the
thermal SZ signal). Since velocities should be unbiased on large scales, the
kSZ signal is an unbiased tracer of the large-scale electron distribution, and
thus can be used to detect the "missing baryon" that evade most observational
techniques. While most current methods for kSZ extraction rely on the
availability of very accurate redshifts, we revisit a method that allows
measurements even in the absence of redshift information for individual
objects. It involves cross-correlating the square of an appropriately filtered
cosmic microwave background (CMB) temperature map with a projected density map
constructed from a sample of large-scale structure tracers. We show that this
method will achieve high signal-to-noise when applied to the next generation of
high-resolution CMB experiments, provided that component separation is
sufficiently effective at removing foreground contamination. Considering
statistical errors only, we forecast that this estimator can yield 3, 120 and over 150 for Planck, Advanced ACTPol, and hypothetical Stage-IV
CMB experiments, respectively, in combination with a galaxy catalog from WISE,
and about 20% larger for a galaxy catalog from the proposed SPHEREx
experiment. This work serves as a companion paper to the first kSZ measurement
with this method, where we used CMB temperature maps constructed from Planck
and WMAP data, together with galaxies from the WISE survey, to obtain a 3.8 -
4.5 detection of the kSZ amplitude.Comment: 14 pages, 10 figures. Comments welcom
The Kinematic Sunyaev-Zel'dovich Effect with Projected Fields: A Novel Probe of the Baryon Distribution with Planck, WMAP, and WISE Data
The kinematic Sunyaev-Zel'dovich (kSZ) effect --- the Doppler boosting of
cosmic microwave background (CMB) photons due to Compton-scattering off free
electrons with non-zero bulk velocity --- probes the abundance and distribution
of baryons in the Universe. All kSZ measurements to date have explicitly
required spectroscopic redshifts. Here, we implement a novel estimator for the
kSZ -- large-scale structure cross-correlation based on projected fields: it
does not require redshift estimates for individual objects, allowing kSZ
measurements from large-scale imaging surveys. We apply this estimator to
cleaned CMB temperature maps constructed from Planck and Wilkinson Microwave
Anisotropy Probe data and a galaxy sample from the Wide-field Infrared Survey
Explorer (WISE). We measure the kSZ effect at 3.8-4.5 significance,
depending on the use of additional WISE galaxy bias constraints. We verify that
our measurements are robust to possible dust emission from the WISE galaxies.
Assuming the standard CDM cosmology, we directly constrain (statistical error
only) at redshift , where is the fraction of matter in
baryonic form and is the free electron fraction. This is the
tightest kSZ-derived constraint reported to date on these parameters. The
consistency between the value found here and the values inferred from
analyses of the primordial CMB and Big Bang nucleosynthesis verifies that
baryons approximately trace the dark matter distribution down to Mpc
scales. While our projected-field estimator is already competitive with other
kSZ approaches when applied to current datasets (because we are able to use the
full-sky WISE photometric survey), it will yield enormous signal-to-noise when
applied to upcoming high-resolution, multi-frequency CMB surveys.Comment: 5 pages + references, 2 figures; v2: matches PRL accepted version,
results unchange
Editorial: Insights into structural and functional organization of the brain: evidence from neuroimaging and non-invasive brain stimulation techniques
The brain is a complex and dynamic system that underlies our behavior, emotions,
and cognition (1–3). To better understand the structural and functional organization of
the brain, neuroimaging and brain stimulation techniques have emerged as powerful tools
(Nyatega et al.) (4–9)
Improved Modeling of the Kinematic Sunyaev-Zel'dovich Projected-Fields signal and its Cosmological Dependence
Over the past decade, the kinematic Sunyaev-Zel'dovich (kSZ) effect has
emerged as an observational probe of the distribution of baryons and velocity
fields in the late Universe. Of the many ways to detect the kSZ, the
'projected-fields kSZ estimator' has the promising feature of not being limited
to galaxy samples with accurate redshifts. The current theoretical modeling of
this estimator involves an approximate treatment only applicable at small
scales. As the measurement fidelity rapidly improves, we find it necessary to
move beyond the original treatment and hence derive an improved theoretical
model for this estimator without these previous approximations. We show that
the differences between the predicted signal from the two models are
scale-dependent and will be significant for future measurements from the Simons
Observatory and CMB-S4 in combination with galaxy data from WISE or the Rubin
Observatory, which have high forecasted signal-to-noise ratios (). Thus,
adopting our improved model in future analyses will be important to avoid
biases. Equipped with our model, we explore the cosmological dependence of this
kSZ signal for future measurements. With a Planck prior, residual uncertainty
on CDM parameters leads to marginalized uncertainties on the
signal amplitude, compared to a sub-percent level forecasted with a fixed
cosmology. To illustrate the potential of this kSZ estimator as a cosmological
probe, we forecast initial constraints on CDM parameters and the sum
of neutrino masses, paving the way for jointly fitting both baryonic
astrophysics and cosmology in future analyses.Comment: 18 pages, 6 figures, submitted to Phys. Rev.
Taking the Universe's Temperature with Spectral Distortions of the Cosmic Microwave Background
The cosmic microwave background (CMB) energy spectrum is a near-perfect
blackbody. The standard model of cosmology predicts small spectral distortions
to this form, but no such distortion of the sky-averaged CMB spectrum has yet
been measured. We calculate the largest expected distortion, which arises from
the inverse Compton scattering of CMB photons off hot, free electrons, known as
the thermal Sunyaev-Zel'dovich (tSZ) effect. We show that the predicted signal
is roughly one order of magnitude below the current bound from the COBE-FIRAS
experiment, but can be detected at enormous significance ()
by the proposed Primordial Inflation Explorer (PIXIE). Although cosmic variance
reduces the effective signal-to-noise to , this measurement will
still yield a sub-percent constraint on the total thermal energy of electrons
in the observable universe. Furthermore, we show that PIXIE can detect subtle
relativistic effects in the sky-averaged tSZ signal at , which
directly probe moments of the optical depth-weighted intracluster medium
electron temperature distribution. These effects break the degeneracy between
the electron density and temperature in the mean tSZ signal, allowing a direct
inference of the mean baryon density at low redshift. Future spectral
distortion probes will thus determine the global thermodynamic properties of
ionized gas in the universe with unprecedented precision. These measurements
will impose a fundamental "integral constraint" on models of galaxy formation
and the injection of feedback energy over cosmic time.Comment: 4.5 pages + references, 2 figures, comments welcome; v2: references
updated; v3: matches PRL accepted versio
W-FYD: a Wearable Fabric-based Display for Haptic Multi-Cue Delivery and Tactile Augmented Reality
Despite the importance of softness, there is no evidence of wearable haptic systems able to deliver controllable softness cues. Here, we present the Wearable Fabric Yielding Display (W-FYD), a fabric-based display for multi-cue delivery that can be worn on user's finger and enables, for the first time, both active and passive softness exploration. It can also induce a sliding effect under the finger-pad. A given stiffness profile can be obtained by modulating the stretching state of the fabric through two motors. Furthermore, a lifting mechanism allows to put the fabric in contact with the user's finger-pad, to enable passive softness rendering. In this paper, we describe the architecture of W-FYD, and a thorough characterization of its stiffness workspace, frequency response and softness rendering capabilities. We also computed device Just Noticeable Difference in both active and passive exploratory conditions, for linear and non-linear stiffness rendering as well as for sliding direction perception. The effect of device weight was also considered. Furthermore, performance of participants and their subjective quantitative evaluation in detecting sliding direction and softness discrimination tasks are reported. Finally, applications of W-FYD in tactile augmented reality for open palpation are discussed, opening interesting perspectives in many fields of human-machine interaction
The spatial effect of fearful faces in the autonomic response
Peripersonal space (PPS) corresponds to the space around the body and it is defined by the location in space where multimodal inputs from bodily and external stimuli are integrated. Its extent varies according to the characteristics of external stimuli, e.g. the salience of an emotional facial expression.
In the present study, we investigated the psycho-physiological correlates of the extension phenomenon. Specifically, we investigated whether an approaching human face showing either an emotionally negative (fearful) or positive (joyful) facial expression would differentially modulate PPS representation, compared to the same face with a neutral expression. To this aim, we continuously recorded the skin conductance response (SCR) of 27 healthy participants while they watched approaching 3D avatar faces showing fearful, joyful or neutral expressions, and then pressed a button to respond to tactile stimuli delivered on their cheeks at three possible delays (visuo-tactile trials).
The results revealed that the SCR to fearful faces, but not joyful or neutral faces, was modulated by the apparent distance from the participant\u2019s body. SCR increased from very far space to far and then to near space. We propose that the proximity of the fearful face provided a cue to the presence of a threat in the environment and elicited a robust and urgent organization of defensive responses. In contrast, there would be no need to organize defensive responses to joyful or neutral faces and, as a consequence, no SCR differences were found across spatial positions. These results confirm the defensive function of PPS
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