34 research outputs found
The dipole of the galaxy bispectrum
The bispectrum will play an important role in future galaxy surveys. On large
scales it is a key probe for measuring primordial non-Gaussianity which can
help differentiate between different inflationary models and other theories of
the early universe. On these scales a variety of relativistic effects come into
play once the galaxy number-count fluctuation is projected onto our past
lightcone. We show for the first time that the leading relativistic correction
from these distortions in the galaxy bispectrum generates a significant dipole,
mainly from relativistic redshift space distortions. The amplitude of the
dipole can be more than 10% of the monopole even on equality scales. Such a
dipole is absent in the Newtonian approximation to the redshift space
bispectrum, so it offers a clear signature of relativistic effects on
cosmological scales in large scale structure.Comment: 5 pages, 2 figures. v2 has slight changes to the figures and is the
version to appear in MNRAS Letter
Temporal Brain Dynamics of Multiple Object Processing: The Flexibility of Individuation
The ability to process concurrently multiple visual objects is fundamental for a coherent perception of the world. A core component of this ability is the simultaneous individuation of multiple objects. Many studies have addressed the mechanism of object individuation but it remains unknown whether the visual system mandatorily individuates all relevant elements in the visual field, or whether object indexing depends on task demands. We used a neural measure of visual selection, the N2pc component, to evaluate the flexibility of multiple object individuation. In three ERP experiments, participants saw a variable number of target elements among homogenous distracters and performed either an enumeration task (Experiment 1) or a detection task, reporting whether at least one (Experiment 2) or a specified number of target elements (Experiment 3) was present. While in the enumeration task the N2pc response increased as a function of the number of targets, no such modulation was found in Experiment 2, indicating that individuation of multiple targets is not mandatory. However, a modulation of the N2pc similar to the enumeration task was visible in Experiment 3, further highlighting that object individuation is a flexible mechanism that binds indexes to object properties and locations as needed for further object processing
Development of a kinetic metabolic model: application to Catharanthus roseus hairy root
A kinetic metabolic model describing Catharanthus roseus hairy root growth and nutrition was developed. The metabolic network includes glycolysis, pentose-phosphate pathway, TCA cycle and the catabolic reactions leading to cell building blocks such as amino acids, organic acids, organic phosphates, lipids and structural hexoses. The central primary metabolic network was taken at pseudo-steady state and metabolic flux analysis technique allowed reducing from 31 metabolic fluxes to 20 independent pathways. Hairy root specific growth rate was described as a function of intracellular concentration in cell building blocks. Intracellular transport and accumulation kinetics for major nutrients were included. The model uses intracellular nutrients as well as energy shuttles to describe metabolic regulation. Model calibration was performed using experimental data obtained from batch and medium exchange liquid cultures of C. roseus hairy root using a minimal medium in Petri dish. The model is efficient in estimating the growth rate
Proteasomal Degradation of TRIM5α during Retrovirus Restriction
The host protein TRIM5α inhibits retroviral infection at an early post-penetration stage by targeting the incoming viral capsid. While the detailed mechanism of restriction remains unclear, recent studies have implicated the activity of cellular proteasomes in the restriction of retroviral reverse transcription imposed by TRIM5α. Here, we show that TRIM5α is rapidly degraded upon encounter of a restriction-susceptible retroviral core. Inoculation of TRIM5α-expressing human 293T cells with a saturating level of HIV-1 particles resulted in accelerated degradation of the HIV-1-restrictive rhesus macaque TRIM5α protein but not the nonrestrictive human TRIM5α protein. Exposure of cells to HIV-1 also destabilized the owl monkey restriction factor TRIMCyp; this was prevented by addition of the inhibitor cyclosporin A and was not observed with an HIV-1 virus containing a mutation in the capsid protein that relieves restriction by TRIMCyp IVHIV. Likewise, human TRIM5α was rapidly degraded upon encounter of the restriction-sensitive N-tropic murine leukemia virus (N-MLV) but not the unrestricted B-MLV. Pretreatment of cells with proteasome inhibitors prevented the HIV-1-induced loss of both rhesus macaque TRIM5α and TRIMCyp proteins. We also detected degradation of endogenous TRIM5α in rhesus macaque cells following HIV-1 infection. We conclude that engagement of a restriction-sensitive retrovirus core results in TRIM5α degradation by a proteasome-dependent mechanism
Delays without Mistakes: Response Time and Error Distributions in Dual-Task
BACKGROUND: When two tasks are presented within a short interval, a delay in the execution of the second task has been systematically observed. Psychological theorizing has argued that while sensory and motor operations can proceed in parallel, the coordination between these modules establishes a processing bottleneck. This model predicts that the timing but not the characteristics (duration, precision, variability...) of each processing stage are affected by interference. Thus, a critical test to this hypothesis is to explore whether the quality of the decision is unaffected by a concurrent task. METHODOLOGY/PRINCIPAL FINDINGS: In number comparison--as in most decision comparison tasks with a scalar measure of the evidence--the extent to which two stimuli can be discriminated is determined by their ratio, referred as the Weber fraction. We investigated performance in a rapid succession of two non-symbolic comparison tasks (number comparison and tone discrimination) in which error rates in both tasks could be manipulated parametrically from chance to almost perfect. We observed that dual-task interference has a massive effect on RT but does not affect the error rates, or the distribution of errors as a function of the evidence. CONCLUSIONS/SIGNIFICANCE: Our results imply that while the decision process itself is delayed during multiple task execution, its workings are unaffected by task interference, providing strong evidence in favor of a sequential model of task execution
SUMO-Interacting Motifs of Human TRIM5α are Important for Antiviral Activity
Human TRIM5α potently restricts particular strains of murine leukemia viruses
(the so-called N-tropic strains) but not others (the B- or NB-tropic strains)
during early stages of infection. We show that overexpression of SUMO-1 in human
293T cells, but not in mouse MDTF cells, profoundly blocks N-MLV infection. This
block is dependent on the tropism of the incoming virus, as neither B-, NB-, nor
the mutant R110E of N-MLV CA (a B-tropic switch) are affected by SUMO-1
overexpression. The block occurred prior to reverse transcription and could be
abrogated by large amounts of restricted virus. Knockdown of TRIM5α in 293T
SUMO-1-overexpressing cells resulted in ablation of the SUMO-1 antiviral
effects, and this loss of restriction could be restored by expression of a human
TRIM5α shRNA-resistant plasmid. Amino acid sequence analysis of human
TRIM5α revealed a consensus SUMO conjugation site at the N-terminus and
three putative SUMO interacting motifs (SIMs) in the B30.2 domain. Mutations of
the TRIM5α consensus SUMO conjugation site did not affect the antiviral
activity of TRIM5α in any of the cell types tested. Mutation of the SIM
consensus sequences, however, abolished TRIM5α antiviral activity against
N-MLV. Mutation of lysines at a potential site of SUMOylation in the CA region
of the Gag gene reduced the SUMO-1 block and the TRIM5α restriction of
N-MLV. Our data suggest a novel aspect of TRIM5α-mediated restriction, in
which the presence of intact SIMs in TRIM5α, and also the SUMO conjugation
of CA, are required for restriction. We propose that at least a portion of the
antiviral activity of TRIM5α is mediated through the binding of its SIMs to
SUMO-conjugated CA
Multipoles of the relativistic galaxy bispectrum
Above the equality scale the galaxy bispectrum will be a key probe for
measuring primordial non-Gaussianity which can help differentiate between
different inflationary models and other theories of the early universe. On
these scales a variety of relativistic effects come into play once the galaxy
number-count fluctuation is projected onto our past lightcone. By decomposing
the Fourier-space bispectrum into invariant multipoles about the observer's
line of sight we examine in detail how the relativistic effects contribute to
these. We show how to perform this decomposition analytically, which is
significantly faster for subsequent computations. While all multipoles receive
a contribution from the relativistic part, odd multipoles arising from the
imaginary part of the bispectrum have no Newtonian contribution, making the odd
multipoles a smoking gun for a relativistic signature in the bispectrum for
single tracers. The dipole and the octopole are significant on equality scales
and above where the Newtonian approximation breaks down. This breakdown is
further signified by the fact that the even multipoles receive a significant
correction on very large scales.Comment: v3 has improved presentation. Version accepted by JCA