1,216 research outputs found
GeNN: a code generation framework for accelerated brain simulations
Large-scale numerical simulations of detailed brain circuit models are important for identifying hypotheses on brain functions and testing their consistency and plausibility. An ongoing challenge for simulating realistic models is, however, computational speed. In this paper, we present the GeNN (GPU-enhanced Neuronal Networks) framework, which aims to facilitate the use of graphics accelerators for computational models of large-scale neuronal networks to address this challenge. GeNN is an open source library that generates code to accelerate the execution of network simulations on NVIDIA GPUs, through a flexible and extensible interface, which does not require in-depth technical knowledge from the users. We present performance benchmarks showing that 200-fold speedup compared to a single core of a CPU can be achieved for a network of one million conductance based Hodgkin-Huxley neurons but that for other models the speedup can differ.
GeNN is available for Linux, Mac OS X and Windows platforms. The source code, user manual, tutorials,
Wiki, in-depth example projects and all other related information can be found on the project website http://genn-team.github.io/genn/
Atomic structure and segregation in alkali-metal heteroclusters
The ground-state atomic and electronic distributions in NamCsn clusters with composition m=n and m=2n have been calculated by minimizing the total cluster energy using the density-functional formalism. The approximation is made by replacing the total external potential of the ions by its spherical average around the cluster center during the iterative process of solving the Kohn-Sham equations for each geometry tested. In the size range studied here (up to 90 atoms per cluster), the cluster is composed of well-separated homoatomic Na and Cs shells, the external one always being a Cs shell. We have also found that the cohesive energy goes rapidly to the bulk limit. An analysis of the geometries shows strong cluster reconstruction with increasing size. By comparing the geometry of pure Nan with that of the Nan core in NanCsn for clusters formed by only an inner Na layer and an outer Cs layer, we have observed that the Nan core adopts a geometry different in most cases from that of the free Nan cluster, and such that the number of faces of the polyhedron formed by the Nan core is as close as possible to the number of external Cs atoms, in order to accomodate these Cs atoms on top of the faces of the polyhedron
DLK1 Is a Somato-Dendritic Protein Expressed in Hypothalamic Arginine-Vasopressin and Oxytocin Neurons
Delta-Like 1 Homolog, Dlk1, is a paternally imprinted gene encoding a transmembrane protein involved in the differentiation of several cell types. After birth, Dlk1 expression decreases substantially in all tissues except endocrine glands. Dlk1 deletion in mice results in pre-natal and post-natal growth deficiency, mild obesity, facial abnormalities, and abnormal skeletal development, suggesting involvement of Dlk1 in perinatal survival, normal growth and homeostasis of fat deposition. A neuroendocrine function has also been suggested for DLK1 but never characterised. To evaluate the neuroendocrine function of DLK1, we first characterised Dlk1 expression in mouse hypothalamus and then studied post-natal variations of the hypothalamic expression. Western Blot analysis of adult mouse hypothalamus protein extracts showed that Dlk1 was expressed almost exclusively as a soluble protein produced by cleavage of the extracellular domain. Immunohistochemistry showed neuronal DLK1 expression in the suprachiasmatic (SCN), supraoptic (SON), paraventricular (PVN), arcuate (ARC), dorsomedial (DMN) and lateral hypothalamic (LH) nuclei. DLK1 was expressed in the dendrites and perikarya of arginine-vasopressin neurons in PVN, SCN and SON and in oxytocin neurons in PVN and SON. These findings suggest a role for DLK1 in the post-natal development of hypothalamic functions, most notably those regulated by the arginine-vasopressin and oxytocin systems
Dlk1 Is Necessary for Proper Skeletal Muscle Development and Regeneration
Delta-like 1homolog (Dlk1) is an imprinted gene encoding a transmembrane protein whose increased expression has been associated with muscle hypertrophy in animal models. However, the mechanisms by which Dlk1 regulates skeletal muscle plasticity remain unknown. Here we combine conditional gene knockout and over-expression analyses to investigate the role of Dlk1 in mouse muscle development, regeneration and myogenic stem cells (satellite cells). Genetic ablation of Dlk1 in the myogenic lineage resulted in reduced body weight and skeletal muscle mass due to reductions in myofiber numbers and myosin heavy chain IIB gene expression. In addition, muscle-specific Dlk1 ablation led to postnatal growth retardation and impaired muscle regeneration, associated with augmented myogenic inhibitory signaling mediated by NF-κB and inflammatory cytokines. To examine the role of Dlk1 in satellite cells, we analyzed the proliferation, self-renewal and differentiation of satellite cells cultured on their native host myofibers. We showed that ablation of Dlk1 inhibits the expression of the myogenic regulatory transcription factor MyoD, and facilitated the self-renewal of activated satellite cells. Conversely, Dlk1 over-expression inhibited the proliferation and enhanced differentiation of cultured myoblasts. As Dlk1 is expressed at low levels in satellite cells but its expression rapidly increases upon myogenic differentiation in vitro and in regenerating muscles in vivo, our results suggest a model in which Dlk1 expressed by nascent or regenerating myofibers non-cell autonomously promotes the differentiation of their neighbor satellite cells and therefore leads to muscle hypertrophy
Observation of Cabibbo-suppressed two-body hadronic decays and precision mass measurement of the baryon
The first observation of the singly Cabibbo-suppressed
and decays
is reported, using proton-proton collision data at a centre-of-mass energy of
, corresponding to an integrated luminosity of , collected with the LHCb detector between 2016 and 2018. The
branching fraction ratios are measured to be
,
. In addition, using the
decay channel, the baryon
mass is measured to be , improving the
precision of the previous world average by a factor of four.Comment: All figures and tables, along with any supplementary material and
additional information, are available at
https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2023-011.html (LHCb
public pages
Measurement of boson production cross-section in collisions at TeV
The first measurement of the boson production cross-section at
centre-of-mass energy TeV in the forward region is reported,
using collision data collected by the LHCb experiment in year 2017,
corresponding to an integrated luminosity of . The
production cross-section is measured for final-state muons in the
pseudorapidity range . The integrated cross-section is determined to be for the di-muon invariant
mass in the range . This result and the
differential cross-section results are in good agreement with theoretical
predictions at next-to-next-to-leading order in the strong coupling.
Based on a previous LHCb measurement of the boson production
cross-section in Pb collisions at TeV, the nuclear
modification factor is measured for the first time at this
energy. The measured values are in the forward region () and
in the backward region
(), where represents the muon rapidity in
the centre-of-mass frame.Comment: All figures and tables, along with any supplementary material and
additional information, are available at
https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2023-010.html (LHCb
public pages
Study of charmonium decays to in the channels
A study of the and decays
is performed using proton-proton collisions at center-of-mass energies of 7, 8
and 13 TeV at the LHCb experiment. The invariant mass spectra from
both decay modes reveal a rich content of charmonium resonances. New precise
measurements of the and resonance parameters are
performed and branching fraction measurements are obtained for decays to
, , and resonances. In particular, the
first observation and branching fraction measurement of is reported as well as first measurements of the
and branching fractions. Dalitz plot analyses of
and decays are performed. A
new measurement of the amplitude and phase of the -wave as functions
of the mass is performed, together with measurements of the
, and parameters. Finally, the branching
fractions of decays to resonances are also measured.Comment: All figures and tables, along with any supplementary material and
additional information, are available at
https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-051.html (LHCb
public pages
Studies of and production in and Pb collisions
The production of and mesons is studied in proton-proton and
proton-lead collisions collected with the LHCb detector. Proton-proton
collisions are studied at center-of-mass energies of and ,
and proton-lead collisions are studied at a center-of-mass energy per nucleon
of . The studies are performed in center-of-mass rapidity
regions (forward rapidity) and
(backward rapidity) defined relative to the proton beam direction. The
and production cross sections are measured differentially as a function
of transverse momentum for and , respectively. The differential cross sections are used to
calculate nuclear modification factors. The nuclear modification factors for
and mesons agree at both forward and backward rapidity, showing
no significant evidence of mass dependence. The differential cross sections of
mesons are also used to calculate cross section ratios,
which show evidence of a deviation from the world average. These studies offer
new constraints on mass-dependent nuclear effects in heavy-ion collisions, as
well as and meson fragmentation.Comment: All figures and tables, along with machine-readable versions and any
supplementary material and additional information, are available at
https://lhcbproject.web.cern.ch/Publications/p/LHCb-PAPER-2023-030.html (LHCb
public pages
Test of lepton flavour universality using decays with hadronic channels
The branching fraction is
measured relative to that of the normalisation mode using hadronic decays in proton-proton collision data
at a centre-of-mass energy of 13 TeV collected by the LHCb experiment,
corresponding to an integrated luminosity of 2 fb. The measured ratio is
, where the first
uncertainty is statistical and the second is related to systematic effects.
Using established branching fractions for the
and modes, the lepton universality test,
is
calculated,
where the third uncertainty is due to the uncertainties on the external
branching fractions. This result is consistent with the Standard Model
prediction and with previous measurements.Comment: All figures and tables, along with machine-readable versions and any
supplementary material and additional information, are available at
https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-052.html (LHCb
public pages
Observation of the decays
This paper reports the observation of the decays using proton-proton collision data collected by the
LHCb experiment, corresponding to an integrated luminosity of
. The branching fractions of these decays are measured
relative to the normalisation channel .
The meson is reconstructed in the
decay channel and the products of branching
fractions are measured to be The first uncertainty is
statistical, the second systematic, and the third arises from the uncertainty
of the branching fraction of the
normalisation channel. The last uncertainty in the result is due to
the limited knowledge of the fragmentation fraction ratio, . The
significance for the and signals is larger than
. The ratio of the helicity amplitudes which governs the angular
distribution of the decay
is determined from the data. The ratio of the - and -wave amplitudes is
found to be and its phase rad,
where the first uncertainty is statistical and the second systematic.Comment: All figures and tables, along with machine-readable versions and any
supplementary material and additional information, are available at
https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2023-014.html (LHCb
public pages
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