13,630 research outputs found
IFN-gamma-mediated suppression of coronavirus replication in glial-committed progenitor cells.
The neurotropic JHM strain of mouse hepatitis virus (JHMV) replicates primarily within glial cells following intracranial inoculation of susceptible mice, with relative sparing of neurons. This study demonstrates that glial cells derived from neural progenitor cells are susceptible to JHMV infection and that treatment of infected cells with IFN-gamma inhibits viral replication in a dose-dependent manner. Although type I IFN production is muted in JHMV-infected glial cultures, IFN-beta is produced following IFN-gamma-treatment of JHMV-infected cells. Also, direct treatment of infected glial cultures with recombinant mouse IFN-alpha or IFN-beta inhibits viral replication. IFN-gamma-mediated control of JHMV replication is dampened in glial cultures derived from the neural progenitor cells of type I receptor knock-out mice. These data indicate that JHMV is capable of infecting glial cells generated from neural progenitor cells and that IFN-gamma-mediated control of viral replication is dependent, in part, on type I IFN secretion
It's all about timing : an electrophysiological examination of feedback-based learning with immediate and delayed feedback
Feedback regarding an individual's action can occur immediately or with a temporal delay. Processing of feedback that varies in its delivery time is proposed to engage different brain mechanisms. fMRI data implicate the striatum in the processing of immediate feedback, and the medial temporal lobe (MTL) in the processing of delayed feedback. The present study offers an electrophysiological examination of feedback processing in the context of timing, by studying the effects of feedback timing on the feedback-related negativity (FRN), a product of the midbrain dopamine system, and elucidating whether the N170 ERP component could capture MTL activation associated with the processing of delayed feedback. Participants completed a word-object paired association learning task; they received feedback 500 ms (immediate feedback condition) following a button press during the learning of two sets of 14 items, and at a delay of 6500 ms (delayed feedback condition) during the learning of the other two sets. The results indicated that while learning outcomes did not differ under the two timing conditions, Event Related Potential (ERPs) pointed to differential activation of the examined ERP components. FRN amplitude was found to be larger following the immediate feedback condition when compared with the delayed feedback condition, and sensitive to valence and learning only under the immediate feedback condition. Additionally, the amplitude of the N170 was found larger following the delayed feedback condition when compared with the immediate feedback condition. Taken together, the findings of the present study support the contention that the processing of delayed feedback involves a shift away from midbrain dopamine activation to the recruitment of the MTL
On the formation and physical properties of the Intra-Cluster Light in hierarchical galaxy formation models
We study the formation of the Intra-Cluster Light (ICL) using a semi-analytic
model of galaxy formation, coupled to merger trees extracted from N-body
simulations of groups and clusters. We assume that the ICL forms by (1) stellar
stripping of satellite galaxies and (2) relaxation processes that take place
during galaxy mergers. The fraction of ICL in groups and clusters predicted by
our models ranges between 10 and 40 per cent, with a large halo-to-halo scatter
and no halo mass dependence. We note, however, that our predicted ICL fractions
depend on the resolution: for a set of simulations with particle mass one order
of magnitude larger than that adopted in the high resolution runs used in our
study, we find that the predicted ICL fractions are ~30-40 per cent larger than
those found in the high resolution runs. On cluster scale, large part of the
scatter is due to a range of dynamical histories, while on smaller scale it is
driven by individual accretion events and stripping of very massive satellites,
, that we find to be the major contributors
to the ICL. The ICL in our models forms very late (below ), and a
fraction varying between 5 and 25 per cent of it has been accreted during the
hierarchical growth of haloes. In agreement with recent observational
measurements, we find the ICL to be made of stars covering a relatively large
range of metallicity, with the bulk of them being sub-solar.Comment: Accepted for Publication in MNRAS, 19 pages, 13 figures, 1 tabl
Using action understanding to understand the left inferior parietal cortex in the human brain
Published in final edited form as: Brain Res. 2014 September 25; 1582: 64–76. doi:10.1016/j.brainres.2014.07.035.Humans have a sophisticated knowledge of the actions that can be performed with objects. In an fMRI study we tried to establish whether this depends on areas that are homologous with the inferior parietal cortex (area PFG) in macaque monkeys. Cells have been described in area PFG that discharge differentially depending upon whether the observer sees an object being brought to the mouth or put in a container. In our study the observers saw videos in which the use of different objects was demonstrated in pantomime; and after viewing the videos, the subject had to pick the object that was appropriate to the pantomime. We found a cluster of activated voxels in parietal areas PFop and PFt and this cluster was greater in the left hemisphere than in the right. We suggest a mechanism that could account for this asymmetry, relate our results to handedness and suggest that they shed light on the human syndrome of apraxia. Finally, we suggest that during the evolution of the hominids, this same pantomime mechanism could have been used to ‘name’ or request objects.We thank Steve Wise for very detailed comments on a draft of this paper. We thank Rogier Mars for help with identifying the areas that were activated in parietal cortex and for comments on a draft of this paper. Finally, we thank Michael Nahhas for help with the imaging figures. This work was supported in part by the NIH grant RO1NS064100 to LMV. (RO1NS064100 - NIH)Accepted manuscrip
Milky Way type galaxies in a LCDM cosmology
We analyse a sample of 52,000 Milky Way (MW) type galaxies drawn from the
publicly available galaxy catalogue of the Millennium Simulation with the aim
of studying statistically the differences and similarities of their properties
in comparison to our Galaxy. Model galaxies are chosen to lie in haloes with
maximum circular velocities in the range 200-250 km/seg and to have
bulge-to-disk ratios similar to that of the Milky Way. We find that model MW
galaxies formed quietly through the accretion of cold gas and small satellite
systems. Only 12 per cent of our model galaxies experienced a major merger
during their lifetime. Most of the stars formed in situ, with only about 15 per
cent of the final mass gathered through accretion. Supernovae and AGN feedback
play an important role in the evolution of these systems. At high redshifts,
when the potential wells of the MW progenitors are shallower, winds driven by
supernovae explosions blow out a large fraction of the gas and metals. As the
systems grow in mass, SN feedback effects decrease and AGN feedback takes over,
playing a more important role in the regulation of the star formation activity
at lower redshifts. Although model Milky Way galaxies have been selected to lie
in a narrow range of maximum circular velocities, they nevertheless exhibit a
significant dispersion in the final stellar masses and metallicities. Our
analysis suggests that this dispersion results from the different accretion
histories of the parent dark matter haloes. Statically, we also find evidences
to support the Milky Way as a typical Sb/Sc galaxy in the same mass range,
providing a suitable benchmark to constrain numerical models of galaxy
formationComment: 10 pages, 7 figures, mne2.cls, MNRAS, replaced with accepted versio
Approximate Methods for State-Space Models
State-space models provide an important body of techniques for analyzing
time-series, but their use requires estimating unobserved states. The optimal
estimate of the state is its conditional expectation given the observation
histories, and computing this expectation is hard when there are
nonlinearities. Existing filtering methods, including sequential Monte Carlo,
tend to be either inaccurate or slow. In this paper, we study a nonlinear
filter for nonlinear/non-Gaussian state-space models, which uses Laplace's
method, an asymptotic series expansion, to approximate the state's conditional
mean and variance, together with a Gaussian conditional distribution. This {\em
Laplace-Gaussian filter} (LGF) gives fast, recursive, deterministic state
estimates, with an error which is set by the stochastic characteristics of the
model and is, we show, stable over time. We illustrate the estimation ability
of the LGF by applying it to the problem of neural decoding and compare it to
sequential Monte Carlo both in simulations and with real data. We find that the
LGF can deliver superior results in a small fraction of the computing time.Comment: 31 pages, 4 figures. Different pagination from journal version due to
incompatible style files but same content; the supplemental file for the
journal appears here as appendices B--E
A scalable hardware and software control apparatus for experiments with hybrid quantum systems
Modern experiments with fundamental quantum systems - like ultracold atoms,
trapped ions, single photons - are managed by a control system formed by a
number of input/output electronic channels governed by a computer. In hybrid
quantum systems, where two or more quantum systems are combined and made to
interact, establishing an efficient control system is particularly challenging
due to the higher complexity, especially when each single quantum system is
characterized by a different timescale. Here we present a new control apparatus
specifically designed to efficiently manage hybrid quantum systems. The
apparatus is formed by a network of fast communicating Field Programmable Gate
Arrays (FPGAs), the action of which is administrated by a software. Both
hardware and software share the same tree-like structure, which ensures a full
scalability of the control apparatus. In the hardware, a master board acts on a
number of slave boards, each of which is equipped with an FPGA that locally
drives analog and digital input/output channels and radiofrequency (RF) outputs
up to 400 MHz. The software is designed to be a general platform for managing
both commercial and home-made instruments in a user-friendly and intuitive
Graphical User Interface (GUI). The architecture ensures that complex control
protocols can be carried out, such as performing of concurrent commands loops
by acting on different channels, the generation of multi-variable error
functions and the implementation of self-optimization procedures. Although
designed for managing experiments with hybrid quantum systems, in particular
with atom-ion mixtures, this control apparatus can in principle be used in any
experiment in atomic, molecular, and optical physics.Comment: 10 pages, 12 figure
Magellan/MMIRS near-infrared multi-object spectroscopy of nebular emission from star forming galaxies at 2<z<3
To investigate the ingredients, which allow star-forming galaxies to present
Lyalpha line in emission, we studied the kinematics and gas phase metallicity
(Z) of the interstellar medium. We used multi-object NIR spectroscopy with
Magellan/MMIRS to study nebular emission from z=2-3 star-forming galaxies
discovered in 3 MUSYC fields. We detected emission lines from four active
galactic nuclei and 13 high-z star-forming galaxies, including Halpha lines
down to a flux of 4.E-17 erg/sec/cm^2. This yielded 7 new redshifts. The most
common emission line detected is [OIII]5007, which is sensitive to Z. We were
able to measure Z for 2 galaxies and to set upper(lower) limits for another
2(2). The Z values are consistent with 0.3<Z/Zsun<1.2. Comparing the Lyalpha
central wavelength with the systemic redshift, we find
Delta_v(Lyalpha-[OIII])=70-270 km/sec. High-redshift star-forming galaxies,
Lyalpha emitting (LAE) galaxies, and Halpha emitters appear to be located in
the low mass, high star-formation rate (SFR) region of the SFR versus stellar
mass diagram, confirming that they are experiencing burst episodes of star
formation, which are building up their stellar mass. Their Zs are consistent
with the relation found for z<2.2 galaxies in the Z versus stellar mass plane.
The measured Delta_v(Lyalpha-[OIII]) values imply that outflows of material,
driven by star formation, could be present in the z=2-3 LAEs of our sample.
Comparing with the literature, we note that galaxies with lower Z than ours are
also characterized by similar Delta_v(Lyalpha-[OIII]) velocity offsets. Strong
[OIII] is detected in many Lyalpha emitters. Therefore, we propose the
Lyalpha/[OIII] flux ratio as a tool for the study of high-z galaxies; while
influenced by Z, ionization, and Lyalpha radiative transfer in the ISM, it may
be possible to calibrate this ratio to primarily trace one of these effects.Comment: 22 pages, 13 figures, 6 table
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