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Neural oscillations during conditional associative learning.
Associative learning requires mapping between complex stimuli and behavioural responses. When multiple stimuli are involved, conditional associative learning is a gradual process with learning based on trial and error. It is established that a distributed network of regions track associative learning, however the role of neural oscillations in human learning remains less clear. Here we used scalp EEG to test how neural oscillations change during learning of arbitrary visuo-motor associations. Participants learned to associative 48 different abstract shapes to one of four button responses through trial and error over repetitions of the shapes. To quantify how well the associations were learned for each trial, we used a state-space computational model of learning that provided a probability of each trial being correct given past performance for that stimulus, that we take as a measure of the strength of the association. We used linear modelling to relate single-trial neural oscillations to single-trial measures of association strength. We found frontal midline theta oscillations during the delay period tracked learning, where theta activity was strongest during the early stages of learning and declined as the associations were formed. Further, posterior alpha and low-beta oscillations in the cue period showed strong desynchronised activity early in learning, while stronger alpha activity during the delay period was seen as associations became well learned. Moreover, the magnitude of these effects during early learning, before the associations were learned, related to improvements in memory seen on the next presentation of the stimulus. The current study provides clear evidence that frontal theta and posterior alpha/beta oscillations play a key role during associative memory formation
Entrainment enhances theta oscillations and improves episodic memory.
Neural oscillations in the theta band have been linked to episodic memory, but it is unclear whether activity patterns that give rise to theta play a causal role in episodic retrieval. Here, we used rhythmic auditory and visual stimulation to entrain neural oscillations to assess whether theta activity contributes to successful memory retrieval. In two separate experiments, human subjects studied words and were subsequently tested on memory for the words ('item recognition') and the context in which each had been previously studied ('source memory'). Between study and test, subjects in the entrainment groups were exposed to audiovisual stimuli designed to enhance activity at 5.5Â Hz, whereas subjects in the control groups were exposed to white noise (Expt. 1) or 14Â Hz entrainment (Expt. 2). Theta entrainment selectively increased source memory performance in both studies. Electroencephalography (EEG) data in Expt. 2 revealed that theta entrainment resulted in band-specific enhancement of theta power during the entrainment period and during post-entrainment memory retrieval. These results demonstrate a direct link between theta activity and episodic memory retrieval. Targeted manipulation of theta activity could be a promising new approach to enhance theta activity and memory performance in healthy individuals and in patients with memory disorders
Chemical Differentiation toward the Pipe Nebula Starless Cores
We used the new IRAM 30-m FTS backend to perform an unbiased ~15 GHz wide
survey at 3 mm toward the Pipe Nebula young diffuse starless cores. We found an
unexpectedly rich chemistry. We propose a new observational classification
based on the 3 mm molecular line emission normalized by the core visual
extinction (Av). Based on this classification, we report a clear
differentiation in terms of chemical composition and of line emission
properties, which served to define three molecular core groups. The "diffuse"
cores, Av<~15, show poor chemistry with mainly simple species (e.g. CS and
CCH). The "oxo-sulfurated" cores, Av~15--22, appear to be abundant in species
like SO and SO2, but also in HCO, which seem to disappear at higher densities.
Finally, the "deuterated" cores, Av>~22, show typical evolved chemistry prior
to the onset of the star formation process, with nitrogenated and deuterated
species, as well as carbon chain molecules. Based on these categories, one of
the "diffuse" cores (Core 47) has the spectral line properties of the
"oxo-sulfurated" ones, which suggests that it is a possible failed core.Comment: Accepted for publication in A&A. 5 pages, 2 figure
Cytoskeletal dynamics and cell signaling during planar polarity establishment in the Drosophila embryonic denticle
Many epithelial cells are polarized along the plane of the epithelium, a property termed planar cell polarity. Th
Importance of the Active Site "Canopy" Residues in an O_2-Tolerant [NiFe]-Hydrogenase
The active site of Hyd-1, an oxygen-tolerant membrane-bound [NiFe]-hydrogenase from Escherichia coli, contains four highly conserved residues that form a âcanopyâ above the bimetallic center, closest to the site at which exogenous agents CO and O_2 interact, substrate H_2 binds, and a hydrido intermediate is stabilized. Genetic modification of the Hyd-1 canopy has allowed the first systematic and detailed kinetic and structural investigation of the influence of the immediate outer coordination shell on H_2 activation. The central canopy residue, arginine 509, suspends a guanidine/guanidinium side chain at close range above the open coordination site lying between the Ni and Fe atoms (Nâmetal distance of 4.4 Ă
): its replacement with lysine lowers the H_2 oxidation rate by nearly 2 orders of magnitude and markedly decreases the H_2/D_2 kinetic isotope effect. Importantly, this collapse in rate constant can now be ascribed to a very unfavorable activation entropy (easily overriding the more favorable activation enthalpy of the R509K variant). The second most important canopy residue for H_2 oxidation is aspartate 118, which forms a salt bridge to the arginine 509 headgroup: its mutation to alanine greatly decreases the H_2 oxidation efficiency, observed as a 10-fold increase in the potential-dependent Michaelis constant. Mutations of aspartate 574 (also salt-bridged to R509) to asparagine and proline 508 to alanine have much smaller effects on kinetic properties. None of the mutations significantly increase sensitivity to CO, but neutralizing the expected negative charges from D118 and D574 decreases O_2 tolerance by stabilizing the oxidized resting Ni^(III)âOH state (âNi-Bâ). An extensive model of the catalytic importance of residues close to the active site now emerges, whereby a conserved gas channel culminates in the arginine headgroup suspended above the Ni and Fe
Reproductive ecology of Lophelia pertusa in Mingulay Reef and the Logachev mounds (North East Atlantic): a multiâscale comparison
This paper presents the results of a multi-scale comparison in the reproductive stage of the cold-water coral Lophelia pertusa in two areas of the North-east Atlantic: The Mingulay Reef and the Logachev Mounds. The study was carried out during the Research cruise âChanging Oceansâ on board of the RRV James Cook, conducted in May-June 2012.
The comparative study between the two geographical areas revealed higher fecundity for the colonies analysed from Mingulay Reef compared to the colonies from the Logachev mounds. Moreover the development stage of the oocytes was more advanced in the colonies sampled from Mingulay than in the ones collected from Logachev.
The comparison between single colonies and within the same colony from the Mingulay Reef did not show any differences in the maturity stage of the oocytes, nevertheless the analyses of the reproductive stage between mesenteries within the same polyps showed high variability, which indicates that the gametogenic development within each mesentery undergoes a prolonged period of oocyte production. This probably results in a protracted spawning period, which might improve the reproductive success of the species.
This work has been developed under the framework of the UKOA program (United Kingdom Ocean Acidification program) and has been supported by the National Environmental Research Council (NERC, UK)
Molecular line profiles as diagnostics of protostellar collapse: modelling the `blue asymmetry' in inside-out infall
The evolution of star-forming core analogues undergoing inside-out collapse
is studied with a multi-point chemodynamical model which self-consistently
computes the abundance distribution of chemical species in the core. For
several collapse periods the output chemistry of infall tracer species such as
HCO+, CS, and N2H+, is then coupled to an accelerated Lambda-iteration
radiative transfer code, which predicts the emerging molecular line profiles
using two different input gas/dust temperature distributions. We investigate
the sensitivity of the predicted spectral line profiles and line asymmetry
ratios to the core temperature distribution, the time-dependent model
chemistry, as well as to ad hoc abundance distributions. The line asymmetry is
found to be strongly dependent on the adopted chemical abundance distribution.
In general, models with a warm central region show higher values of blue
asymmetry in optically thick HCO+ and CS lines than models with a starless core
temperature profile. We find that in the formal context of Shu-type inside-out
infall, and in the absence of rotation or outflows, the relative blue asymmetry
of certain HCO+ and CS transitions is a function of time and, subject to the
foregoing caveats, can act as a collapse chronometer. The sensitivity of
simulated HCO+ line profiles to linear radial variations, subsonic or
supersonic, of the internal turbulence field is investigated in the separate
case of static cores.Comment: Accepted to MNRAS; 20 pages, 13 fig
Gastrointestinal adenocarcinoma incidence and survival trends in South Australia, 1990â2017
Background; Aims: Globally, there has been a concerning rise in the incidence of young-onset cancers. The aim of this study was to provide trends in the incidence and survival of gastrointestinal adenocarcinomas (oesophagus, stomach, pancreas, and colorectal) in South Australia over a 27-year period. Methods: This is a cross-sectional analysis of a prospective longitudinal database including all cases of gastrointestinal adenocarcinomas prospectively reported to the South Australian (State) Cancer Registry from 1990 to 2017. Results: A total of 28,566 patients diagnosed with oesophageal, stomach, pancreatic, or colorectal adenocarcinoma between 1990 and 2017 were included in the study. While the overall incidence for gastrointestinal adenocarcinomas in individuals >50 years has decreased since 2000 (IRR of 0.97 (95% CI 0.94â1.00; p = 0.06)) compared to 1990â1999, the rate amongst individuals aged 18â50 has significantly increased (IRR 1.41 (95% CI 1.27â1.57; p < 0.001)) during the same reference time period. Although noted in both sexes, the rate of increase in incidence was significantly greater in males (11.5 to 19.7/100,000; p < 0.001). The overall survival from adenocarcinomas across all subsites improved in the >50-year cohort in the last decade (HR 0.89 (95% CI 0.86â0.93; p < 0.001)) compared to 1990â1999. In individuals aged 18â50 years, there has only been a significant improvement in survival for colorectal cancer (HR 0.82 (95% CI 0.68â0.99; p < 0.04)), but not the other subsites. A lower overall survival was noted for males in both age cohorts (18â50 yearsâHR 1.24 (95% CI 1.09â1.13; p < 0.01) and >50 yearsâHR 1.13 (95% CI 1.10â1.16; p < 0.001), respectively) compared to females. Conclusions: This study from South Australia demonstrates a significant increase in young-onset gastrointestinal adenocarcinomas over the last 28 years, with a greater increase in the male sex. The only significant improvement in survival in this cohort has been noted in colorectal cancer patients.Dominique Schell, Shahid Ullah, Mark E. Brooke-Smith, Paul Hollington, Marina Yeow, Christos S. Karapetis ... et al
Expressive free speech, the state, and the public sphere: A BakhtinianâDeleuzian analysis of âpublic addressâ at Hyde Park
This is the author's accepted manuscript. The final published article is available from the link below. Copyright @ 2008 Taylor & Francis.In this paper I explore how struggles around free speech between social movements and the state are often underpinned by a deeper struggle around expressive images of what counts as either âdecentâ or âindecentâ discussion. These points are developed by exploring what is arguably the most famous populist place for free speech in Britain, namely Hyde Park. In 1872 the state introduced the Parks Regulation Act in order to regulate, amongst other things, populist uses of free speech at Hyde Park. However, although the 1872 Act designated a site in Hyde Park for public meetings, it did not mention âfree speechâ. Rather, the 1872 Act legally enforced the liberty to make a âpublic addressâ and this was implicitly contrasted by the state of an expressive image of âindecentâ speakers exercising their ârightâ of free speech at Hyde Park. Once constructed, the humiliating image of âindecentâ free speech could then be used by the state to regulate actual utterances of public speakers at Hyde Park. But the paper shows how in the years immediately following 1872 a battle was fought out in Hyde Park over the expressive image of public address between the state and regulars using Hyde Park as a public sphere to exercise free speech. For its part the state had to engage in meaningful deliberative forms of discussion within its own regulatory framework and with the public sphere at Hyde Park in order to maintain the legal form, content and expression of the 1872 Act. To draw out the implications of these points I employ some of the theoretical ideas of the Bakhtin Circle and Gilles Deleuze. Each set of thinkers in their own way make valuable contributions for understanding the relationship between the state, public sphere and expressive images
Search for the standard model Higgs boson in the H to ZZ to 2l 2nu channel in pp collisions at sqrt(s) = 7 TeV
A search for the standard model Higgs boson in the H to ZZ to 2l 2nu decay
channel, where l = e or mu, in pp collisions at a center-of-mass energy of 7
TeV is presented. The data were collected at the LHC, with the CMS detector,
and correspond to an integrated luminosity of 4.6 inverse femtobarns. No
significant excess is observed above the background expectation, and upper
limits are set on the Higgs boson production cross section. The presence of the
standard model Higgs boson with a mass in the 270-440 GeV range is excluded at
95% confidence level.Comment: Submitted to JHE
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