122 research outputs found
Exercising the Tibialis Anterior Muscle of Children with Cerebral Palsy for Improved Neuroplasticity using an Electrical Guitar
Efeitos dos programas de luz sobre desempenho, rendimento de carcaça e resposta imunológica em frangos de corte
A Single-Cell Model for Synaptic Transmission and Plasticity in Human iPSC-Derived Neurons
Synaptic dysfunction is associated with many brain disorders, but robust human cell models to study synaptic transmission and plasticity are lacking. Instead, current in vitro studies on human neurons typically rely on spontaneous synaptic events as a proxy for synapse function. Here, we describe a standardized in vitro approach using human neurons cultured individually on glia microdot arrays that allow single-cell analysis of synapse formation and function. We show that single glutamatergic or GABAergic forebrain neurons differentiated from human induced pluripotent stem cells form mature synapses that exhibit robust evoked synaptic transmission. These neurons show plasticity features such as synaptic facilitation, depression, and recovery. Finally, we show that spontaneous events are a poor predictor of synaptic maturity and do not correlate with the robustness of evoked responses. This methodology can be deployed directly to evaluate disease models for synaptic dysfunction and can be leveraged for drug development and precision medicine. This multisite study by Meijer et al. establishes a standardized in vitro approach to study synapse formation and function in single iPSC-derived human neurons. They validate this approach for GABA and glutamatergic human neurons. The methodology is scalable and suitable for compound screening and disease modeling
The LUX Prototype Detector: Heat Exchanger Development
The LUX (Large Underground Xenon) detector is a two-phase xenon Time
Projection Chamber (TPC) designed to search for WIMP-nucleon dark matter
interactions. As with all noble element detectors, continuous purification of
the detector medium is essential to produce a large (1ms) electron lifetime;
this is necessary for efficient measurement of the electron signal which in
turn is essential for achieving robust discrimination of signal from background
events. In this paper we describe the development of a novel purification
system deployed in a prototype detector. The results from the operation of this
prototype indicated heat exchange with an efficiency above 94% up to a flow
rate of 42 slpm, allowing for an electron drift length greater than 1 meter to
be achieved in approximately two days and sustained for the duration of the
testing period.Comment: 12 pages, 9 figure
Particles-vortex interactions and flow visualization in He4
Recent experiments have demonstrated a remarkable progress in implementing
and use of the Particle Image Velocimetry (PIV) and particle tracking
techniques for the study of turbulence in He4. However, an interpretation of
the experimental data in the superfluid phase requires understanding how the
motion of tracer particles is affected by the two components, the viscous
normal fluid and the inviscid superfluid. Of a particular importance is the
problem of particle interactions with quantized vortex lines which may not only
strongly affect the particle motion, but, under certain conditions, may even
trap particles on quantized vortex cores. The article reviews recent
theoretical, numerical, and experimental results in this rapidly developing
area of research, putting critically together recent results, and solving
apparent inconsistencies. Also discussed is a closely related technique of
detection of quantized vortices negative ion bubbles in He4.Comment: To appear in the J Low Temperature Physic
LUXSim: A Component-Centric Approach to Low-Background Simulations
Geant4 has been used throughout the nuclear and high-energy physics community
to simulate energy depositions in various detectors and materials. These
simulations have mostly been run with a source beam outside the detector. In
the case of low-background physics, however, a primary concern is the effect on
the detector from radioactivity inherent in the detector parts themselves. From
this standpoint, there is no single source or beam, but rather a collection of
sources with potentially complicated spatial extent. LUXSim is a simulation
framework used by the LUX collaboration that takes a component-centric approach
to event generation and recording. A new set of classes allows for multiple
radioactive sources to be set within any number of components at run time, with
the entire collection of sources handled within a single simulation run.
Various levels of information can also be recorded from the individual
components, with these record levels also being set at runtime. This
flexibility in both source generation and information recording is possible
without the need to recompile, reducing the complexity of code management and
the proliferation of versions. Within the code itself, casting geometry objects
within this new set of classes rather than as the default Geant4 classes
automatically extends this flexibility to every individual component. No
additional work is required on the part of the developer, reducing development
time and increasing confidence in the results. We describe the guiding
principles behind LUXSim, detail some of its unique classes and methods, and
give examples of usage.
* Corresponding author, [email protected]: 45 pages, 15 figure
Graph Neural Networks for low-energy event classification & reconstruction in IceCube
IceCube, a cubic-kilometer array of optical sensors built to detect atmospheric and astrophysical neutrinos between 1 GeV and 1 PeV, is deployed 1.45 km to 2.45 km below the surface of the ice sheet at the South Pole. The classification and reconstruction of events from the in-ice detectors play a central role in the analysis of data from IceCube. Reconstructing and classifying events is a challenge due to the irregular detector geometry, inhomogeneous scattering and absorption of light in the ice and, below 100 GeV, the relatively low number of signal photons produced per event. To address this challenge, it is possible to represent IceCube events as point cloud graphs and use a Graph Neural Network (GNN) as the classification and reconstruction method. The GNN is capable of distinguishing neutrino events from cosmic-ray backgrounds, classifying different neutrino event types, and reconstructing the deposited energy, direction and interaction vertex. Based on simulation, we provide a comparison in the 1 GeV–100 GeV energy range to the current state-of-the-art maximum likelihood techniques used in current IceCube analyses, including the effects of known systematic uncertainties. For neutrino event classification, the GNN increases the signal efficiency by 18% at a fixed background rate, compared to current IceCube methods. Alternatively, the GNN offers a reduction of the background (i.e. false positive) rate by over a factor 8 (to below half a percent) at a fixed signal efficiency. For the reconstruction of energy, direction, and interaction vertex, the resolution improves by an average of 13%–20% compared to current maximum likelihood techniques in the energy range of 1 GeV–30 GeV. The GNN, when run on a GPU, is capable of processing IceCube events at a rate nearly double of the median IceCube trigger rate of 2.7 kHz, which opens the possibility of using low energy neutrinos in online searches for transient events.Peer Reviewe
Neutrino oscillation studies with IceCube-DeepCore
AbstractIceCube, a gigaton-scale neutrino detector located at the South Pole, was primarily designed to search for astrophysical neutrinos with energies of PeV and higher. This goal has been achieved with the detection of the highest energy neutrinos to date. At the other end of the energy spectrum, the DeepCore extension lowers the energy threshold of the detector to approximately 10 GeV and opens the door for oscillation studies using atmospheric neutrinos. An analysis of the disappearance of these neutrinos has been completed, with the results produced being complementary with dedicated oscillation experiments. Following a review of the detector principle and performance, the method used to make these calculations, as well as the results, is detailed. Finally, the future prospects of IceCube-DeepCore and the next generation of neutrino experiments at the South Pole (IceCube-Gen2, specifically the PINGU sub-detector) are briefly discussed
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