49 research outputs found
Prefrontal Glutamate Levels Predict Altered Amygdala-prefrontal Connectivity in Traumatized Youths
BACKGROUND:Neurobiological models of stress and stress-related mental illness, including post-traumatic stress disorder, converge on the amygdala and the prefrontal cortex (PFC). While a surge of research has reported altered structural and functional connectivity between amygdala and the medial PFC following severe stress, few have addressed the underlying neurochemistry.METHODS: We combined resting-state functional magnetic resonance imaging measures of amygdala connectivity with in vivo MR-spectroscopy (1H-MRS) measurements of glutamate in 26 survivors from the 2011 Norwegian terror attack and 34 control subjects.RESULTS: Traumatized youths showed altered amygdala-anterior midcingulate cortex (aMCC) and amygdala-ventromedial prefrontal cortex (vmPFC) connectivity. Moreover, the trauma survivors exhibited reduced levels of glutamate in the vmPFC which fits with the previous findings of reduced levels of Glx (glutamate + glutamine) in the aMCC (Ousdal et al.2017) and together suggest long-term impact of a traumatic experience on glutamatergic pathways. Importantly, local glutamatergic metabolite levels predicted the individual amygdala-aMCC and amygdala-vmPFC functional connectivity, and also mediated the observed group difference in amygdala-aMCC connectivity.CONCLUSIONS: Our findings suggest that traumatic stress may influence amygdala-prefrontal neuronal connectivity through an effect on prefrontal glutamate and its compounds. Understanding the neurochemical underpinning of altered amygdala connectivity after trauma may ultimately lead to the discovery of new pharmacological agents which can prevent or treat stress-related mental illness
The impact of traumatic stress on Pavlovian biases
BACKGROUND: Disturbances in Pavlovian valuation systems are reported to follow traumatic stress exposure. However, motivated decisions are also guided by instrumental mechanisms, but to date the effect of traumatic stress on these instrumental systems remain poorly investigated. Here, we examine whether a single episode of severe traumatic stress influences flexible instrumental decisions through an impact on a Pavlovian system. METHODS: Twenty-six survivors of the 2011 Norwegian terror attack and 30 matched control subjects performed an instrumental learning task in which Pavlovian and instrumental associations promoted congruent or conflicting responses. We used reinforcement learning models to infer how traumatic stress affected learning and decision-making. Based on the importance of dorsal anterior cingulate cortex (dACC) for cognitive control, we also investigated if individual concentrations of Glx (=glutamate + glutamine) in dACC predicted the Pavlovian bias of choice. RESULTS: Survivors of traumatic stress expressed a greater Pavlovian interference with instrumental action selection and had significantly lower levels of Glx in the dACC. Across subjects, the degree of Pavlovian interference was negatively associated with dACC Glx concentrations. CONCLUSIONS: Experiencing traumatic stress appears to render instrumental decisions less flexible by increasing the susceptibility to Pavlovian influences. An observed association between prefrontal glutamatergic levels and this Pavlovian bias provides novel insight into the neurochemical basis of decision-making, and suggests a mechanism by which traumatic stress can impair flexible instrumental behaviours
Optimization of thermal design and geometrical parameters of a flat tube-fin adsorbent bed for automobile air-conditioning
Adsorbent bed design and performance strongly affect the overall performance of adsorption systems. In the present study, an analytical model was developed to determine the optimum geometrical and thermal parameters of a flat tube-fin adsorbent bed to reach the maximum system performance. This types of heat exchangers offer substantial reduced in weight, cost, volume and thermal conductivity, which can make them a good choice for adsorbent beds in automobile applications. Results showed that the overall thermal conductance of the bed and the maximum practical specific cooling capacity increased when reducing in flat tube thickness and fin pitch as well as by increasing in fin thickness and water channel wall thickness. The specific thermal conductance increased by 2.5% when reducing the channel pitch from its design value to a minimum permissible (0.004 m). From thermal parameters that have been studied, the adsorbent thermal conductivity is the most sensitive parameter to the specific thermal conductance in beds. The system performance also significantly enhanced by reducing the mass of the metal bed and the heat transfer fluids as well as the desorption heat of the selecting working pair. (C) 2016 Elsevier Ltd. All rights reserved.This work has been partially supported by the Thermally Operated Mobile Air Conditioning Systems (TOPMACS).Verde Trindade, M.; Harby Mohamed Abd Alaal, K.; Corberán, JM. (2017). Optimization of thermal design and geometrical parameters of a flat tube-fin adsorbent bed for automobile air-conditioning. Applied Thermal Engineering. 111:489-502. https://doi.org/10.1016/j.applthermaleng.2016.09.099S48950211
Star cluster formation in the most extreme environments: Insights from the HiPEEC survey
We present the Hubble imaging Probe of Extreme Environments and Clusters
(HiPEEC) survey. We fit HST NUV to NIR broadband and H fluxes, to
derive star cluster ages, masses, extinctions and determine the star formation
rate (SFR) of 6 merging galaxies. These systems are excellent laboratories to
trace cluster formation under extreme gas physical conditions, rare in the
local universe, but typical for star-forming galaxies at cosmic noon. We detect
clusters with ages of 1-500 Myr and masses that exceed M. The
recent cluster formation history and their distribution within the host
galaxies suggest that systems like NGC34, NGC1614, NGC4194 are close to their
final coalescing phase, while NGC3256, NGC3690, NGC6052 are at an
earlier/intermediate stage. A Bayesian analysis of the cluster mass function in
the age interval 1-100 Myr provides strong evidence in 4 of the 6 galaxies that
an exponentially truncated power law better describes the observed mass
distributions. For two galaxies, the fits are inconclusive due to low number
statistics. We determine power-law slopes to , and
truncation masses, M, between and a few times M,
among the highest values reported in the literature. Advanced mergers have
higher M than early/intermediate merger stage galaxies, suggesting rapid
changes in the dense gas conditions during the merger. We compare the total
stellar mass in clusters to the SFR of the galaxy, finding that these systems
are among the most efficient environments to form star clusters in the local
universe.Comment: Accepted for publication in MNRAS; data and catalogues will be
released at this URL http://dx.doi.org/10.17909/t9-cn0b-ht8
Forensic interviewing of mentally disordered suspects: The impact of interview style on investigation outcomes.
The investigative interviewing of a vulnerable suspect is a complex and difficult task. Current best practice advocates for the use of open questions in order to elicit a free recall. However, those with mental health conditions have limited cognitive abilities that relate to free recall and episodic memory, and there is emerging evidence that suggests open questions may not always be most suitable for the vulnerable interviewee. As such, the present study examined the impact of two different interview models (best practice v modified interview) on the amount and accuracy of investigation relevant information obtained within an experimental vulnerable ‘suspect’ sample. Participants engaged in two tasks; a minor transgression and a matched non-transgression. Each participant was then subject to either a best practice (containing largely open questions) or a modified interview (containing largely closed questions). Vulnerable participants provided a significantly higher and more accurate amount of investigation relevant information during the modified interview rather than the best practice interview. In addition, participants that have mental health conditions sought more clarifications during the best practice interviews. The type of interview did not impact upon the level of vulnerability displayed. Our findings challenge current best practice in that vulnerable participants performed worse in interviews containing more open questions than closed questions. These findings add to the emerging evidence base that vulnerable individuals may require an alternative method of questioning, including the use of closed questions as ‘scaffolding’ during an investigative interview
MIDIS. JWST NIRCam and MIRI unveil the stellar population properties of Ly-emitters and Lyman-Break galaxies at z ~ 3-7
We study the stellar population properties of 182 spectroscopically-confirmed
(MUSE/VLT) Lyman- emitters (LAEs) and 450 photometrically-selected
Lyman-Break galaxies (LBGs) at z = 2.8 - 6.7 in the Hubble eXtreme Deep Field
(XDF). Leveraging the combined power of HST and JWST NIRCam and MIRI
observations, we analyse their rest-frame UV-through-near-IR spectral energy
distributions (SEDs) with MIRI playing a crucial role in robustly assessing the
LAE's stellar mass and ages. Our LAEs are low-mass objects
(log(M[M]) ~ 7.5), with little or no dust extinction
(E(B - V) ~ 0.1) and a blue UV continuum slope ( ~ -2.2). While 75% of
our LAEs are young (< 100 Myr), the remaining 25% have significantly older
stellar populations (> 100 Myr). These old LAEs are statistically more massive,
less extinct and have lower specific star formation rate (sSFR) compared to
young LAEs. Besides, they populate the M - SFR plane along the
main-sequence (MS) of star-forming galaxies, while young LAEs populate the
starburst region. The comparison between the LAEs properties to those of a
stellar-mass matched sample of LBGs shows no statistical difference between
these objects, except for the LBGs redder UV continuum slope and marginally
larger E(B - V) values. Interestingly, 48% of the LBGs have ages < 10 Myr and
are classified as starbursts, but lack detectable Ly emission. This is
likely due to HI resonant scattering and/or selective dust extinction. Overall,
we find that JWST observations are crucial in determining the properties of
LAEs and shedding light on the properties and similarities between LAEs and
LBGs.Comment: 19 pages, 15 figures, 5 tables. Submitted to AP
Strong (Hb + [OIII]) and Ha emitters at redshift z ~ 7-8 unveiled with JWST/NIRCam and MIRI imaging in the Hubble eXtreme Deep Field (XDF)
The JWST is revolutionizing the study of high-redshift galaxies by providing
for the first time a high-sensitivity view of the early Universe at infrared
wavelengths, both with its Near Infrared Camera (NIRCam) and Mid Infrared
Instrument (MIRI). In this paper, we make use of medium and broad-band NIRCam
imaging, as well as ultra-deep MIRI 5.6 microns imaging, in the Hubble eXtreme
Deep Field (XDF) to identify prominent line emitters at z ~ 7-8. Out of a total
of 58 galaxies at z ~ 7-8, we find 18 robust candidates (~31%) for prominent
(Hb + [OIII]) emitters, based on their enhanced fluxes in the F430M and F444W
filters, with rest-frame EW(Hb + [OIII]) ~ 87 - 2100 A. Among these emitters,
16 lie on the MIRI coverage area and 12 show a clear flux excess at 5.6
microns, indicating the simultaneous presence of a prominent Ha emission line
with rest-frame EW(Ha) ~ 200 - 3000 A. This is the first time that Ha emission
can be detected in individual galaxies at z>7. The Ha line, when present,
allows us to separate the contributions of the Hb and [OIII] emission lines to
the (Hb + [OIII]) complex and derive Ha-based star formation rates (SFRs). We
find that in some cases [OIII]/Hb > 1, suggesting low metallicities, but a few
have [OIII]/Hb < 1, so the NIRCam flux excess is mainly driven by Hb. The vast
majority of prominent line emitters are very young starbursts or galaxies on
their way to/from the starburst cloud. They make for a cosmic SFR density
log10(SFRD_Ha / Msun yr^-1 Mpc^-3) ~ 2.35, which is about a third of the total
value at z ~ 7-8. Therefore, the strong Ha emitters likely had an important
role in reionization.Comment: 15 pages, 9 figures. Submitted to Ap
Traffic (safety) culture and alcohol use: cultural patterns in the light of results of the SARTRE 4 study
The optically unbiased GRB host (TOUGH) survey. VI. Radio observations at z<1 and consistency with typical star-forming galaxies
The objective of this paper is to determine the level of obscured star
formation activity and dust attenuation in a sample of gamma-ray burst (GRB)
hosts; and to test the hypothesis that GRB hosts have properties consistent
with those of the general star-forming galaxy populations. We present a radio
continuum survey of all z<1 GRB hosts in The Optically Unbiased GRB Host
(TOUGH) sample supplemented with radio data for all (mostly pre-Swift) GRB-SN
hosts discovered before October 2006. We present new radio data for 22 objects
and have obtained a detection for three of them (GRB 980425, 021211, 031203;
none in the TOUGH sample), increasing the number of radio-detected GRB hosts
from two to five. The star formation rate (SFR) for the GRB 021211 host of ~825
Mo yr^-1, the highest ever reported for a GRB host, places it in the category
of ultraluminous infrared galaxies. We found that at least 63% of GRB hosts
have SFR 500 Mo yr^-1. For the
undetected hosts the mean radio flux (<35 uJy 3sigma) corresponds to an average
SFR < 15 Mo yr^-1. Moreover, ~88% of the z<1 GRB hosts have ultraviolet dust
attenuation A_UV < 6.7 mag (visual attenuation A_V < 3 mag). Hence we did not
find evidence for large dust obscuration in a majority of GRB hosts. Finally,
we found that the distributions of SFRs and A_UV of GRB hosts are consistent
with those of Lyman break galaxies, Halpha emitters at similar redshifts and of
galaxies from cosmological simulations. The similarity of the GRB population
with other star-forming galaxies is consistent with the hypothesis that GRBs, a
least at z<1, trace a large fraction of all star formation, and are therefore
less biased indicators than once thought.Comment: Accepted by ApJ. 13 pages, 4 figures, 2 tables. V3: minor changes to
match the published versio