1,687 research outputs found
Individual differences in white matter microstructure reflect variation in functional connectivity during action choice.
The relation between brain structure and function is of fundamental importance in neuroscience. Comparisons between behavioral and brain imaging measures suggest that variation in brain structure correlates with the presence of specific skills[1-3]. Behavioral measures, however, reflect the integrated function of multiple brain regions. Rather than behavior, a physiological index of function could be a more sensitive and informative measure with which to compare structural measures. Here, we test for a relationship between a physiological measure of functional connectivity between two brain areas during a simple decision making task and a measure of structural connectivity. Paired-pulse transcranial magnetic stimulation indexed functional connectivity between two regions important for action choices: premotor and motor cortex. Fractional anisotropy (FA), a marker of microstructural integrity, indexed structural connectivity. Individual differences in functional connectivity during action selection show highly specific correlations with FA in localised regions of white matter interconnecting regions including the premotor and motor cortex. Probabilistic tractography[4, 5], a technique for identifying fibre pathways from diffusion-weighted imaging (DWI), reconstructed the anatomical networks linking the component brain regions involved in making decisions. These findings demonstrate a relationship between individual differences in functional and structural connectivity within human brain networks central to action choice
Modeling the Impact of Baryons on Subhalo Populations with Machine Learning
We identify subhalos in dark matter-only (DMO) zoom-in simulations that are
likely to be disrupted due to baryonic effects by using a random forest
classifier trained on two hydrodynamic simulations of Milky Way (MW)-mass host
halos from the Latte suite of the Feedback in Realistic Environments (FIRE)
project. We train our classifier using five properties of each disrupted and
surviving subhalo: pericentric distance and scale factor at first pericentric
passage after accretion, and scale factor, virial mass, and maximum circular
velocity at accretion. Our five-property classifier identifies disrupted
subhalos in the FIRE simulations with an out-of-bag classification
score. We predict surviving subhalo populations in DMO simulations of the FIRE
host halos, finding excellent agreement with the hydrodynamic results; in
particular, our classifier outperforms DMO zoom-in simulations that include the
gravitational potential of the central galactic disk in each hydrodynamic
simulation, indicating that it captures both the dynamical effects of a central
disk and additional baryonic physics. We also predict surviving subhalo
populations for a suite of DMO zoom-in simulations of MW-mass host halos,
finding that baryons impact each system consistently and that the predicted
amount of subhalo disruption is larger than the host-to-host scatter among the
subhalo populations. Although the small size and specific baryonic physics
prescription of our training set limits the generality of our results, our work
suggests that machine-learning classification algorithms trained on
hydrodynamic zoom-in simulations can efficiently predict realistic subhalo
populations.Comment: 20 pages, 14 figures. Updated to published version. Code available at
https://github.com/ollienad/subhalo_randomfores
Timescales of spike-train correlation for neural oscillators with common drive
We examine the effect of the phase-resetting curve (PRC) on the transfer of
correlated input signals into correlated output spikes in a class of neural
models receiving noisy, super-threshold stimulation. We use linear response
theory to approximate the spike correlation coefficient in terms of moments of
the associated exit time problem, and contrast the results for Type I vs. Type
II models and across the different timescales over which spike correlations can
be assessed. We find that, on long timescales, Type I oscillators transfer
correlations much more efficiently than Type II oscillators. On short
timescales this trend reverses, with the relative efficiency switching at a
timescale that depends on the mean and standard deviation of input currents.
This switch occurs over timescales that could be exploited by downstream
circuits
Solar Neutron Events of October-November 2003
During the period when the Sun was intensely active on October-November 2003,
two remarkable solar neutron events were observed by the ground-based neutron
monitors. On October 28, 2003, in association with an X17.2 large flare, solar
neutrons were detected with high statistical significance (6.4 sigma) by the
neutron monitor at Tsumeb, Namibia. On November 4, 2003, in association with an
X28 class flare, relativistic solar neutrons were observed by the neutron
monitors at Haleakala in Hawaii and Mexico City, and by the solar neutron
telescope at Mauna Kea in Hawaii simultaneously. Clear excesses were observed
at the same time by these detectors, with the significance calculated as 7.5
sigma for Haleakala, and 5.2 sigma for Mexico City. The detector onboard the
INTEGRAL satellite observed a high flux of hard X-rays and gamma-rays at the
same time in these events. By using the time profiles of the gamma-ray lines,
we can explain the time profile of the neutron monitor. It appears that
neutrons were produced at the same time as the gamma-ray emission.Comment: 35 pages, 21 figures, accepted for publication in Ap
Cryogenic Design of a PrFeB Based Undulator
A PrFeB based cryogenic undulator has been built at Helmholtz Zentrum Berlin HZB in collaboration with the Ludwig Maximilian University München LMU . LMU will operate the undulator at a laser plasma accelerator at the Max Planck Institut für Quantenoptik in Garching. The 20 period device has a period length of 9mm and a fixed gap of 2.5mm. The operation of a small gap device at a high emittance electron beam requires stable magnetic material. A high coercivity is achieved with PrFeB material cooled down to 20 30K. In this paper we present the mechanic, magnetic and cryogenic design and compare predictions with measured dat
Dopamine D_2-receptor activation elicits akinesia, rigidity, catalepsy, and tremor in mice expressing hypersensitive 4 nicotinic receptors via a cholinergic-dependent mechanism
Recent studies suggest that high-affinity neuronal nicotinic acetylcholine receptors (nAChRs) containing α4 and β2 subunits (α4β2*) functionally interact with G-protein-coupled dopamine (DA) D_2 receptors in basal ganglia. We hypothesized that if a functional interaction between these receptors exists, then mice expressing an M2 point mutation (Leu9'Ala) rendering 4 nAChRs hypersensitive to ACh may exhibit altered sensitivity to a D_2-receptor agonist. When challenged with the D_(2)R agonist, quinpirole (0.5–10 mg/kg), Leu9'Ala mice, but not wild-type (WT) littermates, developed severe, reversible motor impairment characterized by rigidity, catalepsy, akinesia, and tremor. While striatal DA tissue content, baseline release, and quinpirole-induced DA depletion did not differ between Leu9'Ala and WT mice, quinpirole dramatically increased activity of cholinergic striatal interneurons only in mutant animals, as measured by increased c-Fos expression in choline acetyltransferase (ChAT)-positive interneurons. Highlighting the importance of the cholinergic system in this mouse model, inhibiting the effects of ACh by blocking muscarinic receptors, or by selectively activating hypersensitive nAChRs with nicotine, rescued motor symptoms. This novel mouse model mimics the imbalance between striatal DA/ACh function associated with severe motor impairment in disorders such as Parkinson’s disease, and the data suggest that a D_(2)R–α4*-nAChR functional interaction regulates cholinergic interneuron activity.—Zhao-Shea, R., Cohen, B. N., Just, H., McClure-Begley, T., Whiteaker, P., Grady, S. R., Salminen, O., Gardner, P. D., Lester, H. A., Tapper, A. R. Dopamine D2-receptor activation elicits akinesia, rigidity, catalepsy, and tremor in mice expressing hypersensitive α4 nicotinic receptors via a cholinergic-dependent mechanism
Global warming: is weight loss a solution?
The current climate change has been most likely caused by the increased greenhouse gas emissions. We have looked at the major greenhouse gas, carbon dioxide (CO2), and estimated the reduction in the CO2 emissions that would occur with the theoretical global weight loss. The calculations were based on our previous weight loss study, investigating the effects of a low-carbohydrate diet on body weight, body composition and resting metabolic rate of obese volunteers with type 2 diabetes. At 6 months we observed decreases in weight, fat mass, fat free mass and CO2 production. We estimated that a 10 kg weight loss of all obese and overweight people would result in a decrease of 49.560 Mt of CO2 per year, which would equal to 0.2 % of the CO2 emitted globally in 2007. This reduction could help meet the CO2 emission reduction targets and unquestionably would be of a great benefit to the global health
Deep neural networks allow expert-level brain meningioma segmentation and present potential for improvement of clinical practice
Accurate brain meningioma segmentation and volumetric assessment are critical for serial patient follow-up, surgical planning and monitoring response to treatment. Current gold standard of manual labeling is a time-consuming process, subject to inter-user variability. Fully-automated algorithms for meningioma segmentation have the potential to bring volumetric analysis into clinical and research workflows by increasing accuracy and efficiency, reducing inter-user variability and saving time. Previous research has focused solely on segmentation tasks without assessment of impact and usability of deep learning solutions in clinical practice. Herein, we demonstrate a three-dimensional convolutional neural network (3D-CNN) that performs expert-level, automated meningioma segmentation and volume estimation on MRI scans. A 3D-CNN was initially trained by segmenting entire brain volumes using a dataset of 10,099 healthy brain MRIs. Using transfer learning, the network was then specifically trained on meningioma segmentation using 806 expert-labeled MRIs. The final model achieved a median performance of 88.2% reaching the spectrum of current inter-expert variability (82.6-91.6%). We demonstrate in a simulated clinical scenario that a deep learning approach to meningioma segmentation is feasible, highly accurate and has the potential to improve current clinical practice
538 A.D. and the Transition from Pagan Roman Empire to Holy Roman Empire: Justinian’s Metamorphosis from Chief of Staffs to Theologian
The year 538 A.D. became the turning point in the history of the Roman Empire since so many aspects on political, administrative and economical levels were already switched off that when Justinian declared himself to be a theologian from this year and no longer a soldier, he crossed the barrier of his mandate between what is purely civil obligation and what is religious obligation, similarly to Constantine before, and entered in competition with the papal function and this role is evidence of Justinian’s ongoing caesaro-papism. The quest for unification of the empire by unification of the church, the fever for church-building projects with his wife Theodora, the persecution of enemies of the church and heretics, his disdain with the Sabbath although his second name was Sabbatini, his support for suppressing any eschatological fever in line with the church fathers and Oecumenius and yet trying to build the ‘Kingdom of God’ on earth, all this indicate the problem 538 was for the Roman Empire and the Catholic Church. Archaeological and historical original sources of Justinian and contemporaries of popes, biographer of Justinian and a commentator on Revelation (Oecumenius) are very revealing of these times and the shift or transition of what belonged to the Roman Empire handed over since 538 A.D. to the church and the papal function. The Code of Justinian was a persecuting instrument. Justinian upheld the supremacy of the papacy. He permitted through the Council of Orleans actions to be done on Sunday that Constantine prohibited like travel and preparation of food and cleaning the house. In Novellae CXLIV Justinian instituted a Seventh-day Sabbath persecution. He changed the times and laws ad hoc as his Novellae XLVI and coins of 538 A.D. (XII year) indicate. Private gatherings were persecuted. He had church-manual laws. Justinian studied Systematic Theology on the nature of Christ and wrote homiletical rules for preachers. He gave textcritical advice to Jews and condemned their doctrinal deviations. This theological hobby of the ruler of the once mighty Roman Empire was to be taken over by a more theological competent power that would eventually lead to papal-caesarism until the unsettling of this new aggrandizing paradigm in 1798 by Napoleon. The prophetic embedding of the 1260 days as “years” prophecies in both Daniel 7 and Revelation 12 definitely started in 538 A.D. contrary to W. Spicer’s (1918) suggestion of 533 or 538 as two alternative dates or any other dates suggested by other scholars in the history of interpretation in historicism. It is also not just a case of history of interpretation hermeneutics but data solidly supported by archaeology, iconography and original historical sources that coincides with the parameters provided by exegesis of the rest of the Books of Daniel and Revelation added with the exegesis of the detail of the passages under consideration. A necessary ingredient for the historical researcher remains to be the faith that God can predict the future and He did and that the data as well as the prophecies of the Biblical Text are evidence of that
Superconductivity in Ropes of Single-Walled Carbon Nanotubes
We report measurements on ropes of Single Walled Carbon Nanotubes (SWNT) in
low-resistance contact to non-superconducting (normal) metallic pads, at low
voltage and at temperatures down to 70 mK. In one sample, we find a two order
of magnitude resistance drop below 0.55 K, which is destroyed by a magnetic
field of the order of 1T, or by a d.c. current greater than 2.5 microA. These
features strongly suggest the existence of superconductivity in ropes of SWNT.Comment: Accepted for publication in Phys. Rev. Let
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