35 research outputs found
Ultra low background Micromegas detectors for BabyIAXO solar axion search
The International AXion Observatory (IAXO) is a large scale axion helioscope
that will look for axions and axion-like particles produced in the Sun with
unprecedented sensitivity. BabyIAXO is an intermediate experimental stage that
will be hosted at DESY (Germany) and that will test all IAXO subsystems serving
as a prototype for IAXO but at the same time as a fully-fledged helioscope with
potential for discovery.
One of the crucial components of the project is the ultra-low background
X-ray detectors that will image the X-ray photons produced by axion conversion
in the experiment. The baseline detection technology for this purpose are
Micromegas (Microbulk) detectors. We will show the quest and the strategy to
attain the very challenging levels of background targeted for BabyIAXO that
need a multi-approach strategy coming from ground measurements, screening
campaigns of components of the detector, underground measurements, background
models, in-situ background measurements as well as powerful rejection
algorithms. First results from the commissioning of the BabyIAXO prototype will
be shown.Comment: 4 pages, 2 figures, submitted for the proceedings of the
International Conference on Micro Pattern Gaseous Detectors, December 2022,
Israe
Search for Dark Matter Axions with CAST-CAPP
The CAST-CAPP axion haloscope, operating at CERN inside the CAST dipole
magnet, has searched for axions in the 19.74 eV to 22.47 eV mass
range. The detection concept follows the Sikivie haloscope principle, where
Dark Matter axions convert into photons within a resonator immersed in a
magnetic field. The CAST-CAPP resonator is an array of four individual
rectangular cavities inserted in a strong dipole magnet, phase-matched to
maximize the detection sensitivity. Here we report on the data acquired for
4124 h from 2019 to 2021. Each cavity is equipped with a fast frequency tuning
mechanism of 10 MHz/min between 4.774 GHz and 5.434 GHz. In the present work,
we exclude axion-photon couplings for virialized galactic axions down to
at the 90% confidence
level. The here implemented phase-matching technique also allows for future
large-scale upgrades.Comment: 24 pages, 5 figures, Published version available with Open Access at
https://www.nature.com/articles/s41467-022-33913-
Search for Dark Matter Axions with CAST-CAPP
The CAST-CAPP axion haloscope, operating at CERN inside the CAST dipole magnet, has searched for axions in the 19.74 μeV to 22.47 μeV mass range. The detection concept follows the Sikivie haloscope principle, where Dark Matter axions convert into photons within a resonator immersed in a magnetic field. The CAST-CAPP resonator is an array of four individual rectangular cavities inserted in a strong dipole magnet, phase-matched to maximize the detection sensitivity. Here we report on the data acquired for 4124 h from 2019 to 2021. Each cavity is equipped with a fast frequency tuning mechanism of 10 MHz/ min between 4.774 GHz and 5.434 GHz. In the present work, we exclude axion-photon couplings for virialized galactic axions down to gaγγ = 8 × 10−14 GeV−1 at the 90% confidence level. The here implemented phase-matching technique also allows for future large-scale upgrades
Background discrimination with a Micromegas detector prototype and veto system for BabyIAXO
In this paper we present measurements performed with a Micromegas X-ray detector setup. The detector is a prototype in the context of the BabyIAXO helioscope, which is under construction to search for an emission of the hypothetical axion particle from the Sun. An important component of such a helioscope is a low background X-ray detector with a high efficiency in the 1–10 keV energy range. The goal of the measurement was to study techniques for background discrimination. In addition to common techniques we used a multi-layer veto system designed to tag cosmic-ray induced neutron background. Over an effective time of 52 days, a background level of 8.6 × 10−7 counts keV−1 cm−2 s−1 was reached in a laboratory at above ground level. This is the lowest background level achieved at surface level. In this paper we present the experimental setup, show simulations of the neutron-induced background, and demonstrate the process to identify background signals in the data. Finally, prospects to reach lower background levels down to 10–7 counts keV−1 cm−2 s−1 are discussed
Requirement of enhanced Survival Motoneuron protein imposed during neuromuscular junction maturation
Spinal muscular atrophy is a common motor neuron disease caused by low survival motoneuron (SMN), a key protein in the proper splicing of genes. Restoring the protein is therefore a promising therapeutic strategy. Implementation of this strategy, however, depends on defining the temporal requirements for SMN. Here, we used controlled knockdown of SMN in transgenic mice to determine the precise postnatal stage requirements for this protein. Reducing SMN in neonatal mice resulted in a classic SMA-like phenotype. Unexpectedly, depletion of SMN in adults had relatively little effect. Insensitivity to low SMN emerged abruptly at postnatal day 17, which coincided with establishment of the fully mature neuromuscular junction (NMJ). Mature animals depleted of SMN eventually exhibited evidence of selective neuromuscular pathology that was made worse by traumatic injury. The ability to regenerate the mature NMJ in aged or injured SMN-depleted mice was grossly impaired, a likely consequence of the inability to meet the surge in demand for motoneuronal SMN that was seen in controls. Our results demonstrate that relative maturity of the NMJ determines the temporal requirement for the SMN protein. These observations suggest that the use of potent but potentially deleterious SMN-enhancing agents could be tapered in human patients once the neuromuscular system matures and reintroduced as needed to enhance SMN for remodeling aged or injured NMJs. \ua9 Copyright 2014 American Society for Clinical Investigation
Cellular localization of the atypical isoforms of protein kinase C (aPKCζ/PKMζ and aPKCλ/ι) on the neuromuscular synapse
10.1016/j.neulet.2013.10.00
Adenosine A2B and A3 receptor location at the mouse neuromuscular junction
10.1111/joa.12188To date, four subtypes of adenosine receptors have been cloned (A1R, A2AR, A2BR, and A3R). In a previous study we used confocal immunocytochemistry to identify A1R and A2AR receptors at mouse neuromuscular junctions (NMJs). The data shows that these receptors are localized differently in the three cells (muscle, nerve and glia) that configure the NMJs. A1R localizes in the terminal teloglial Schwann cell and nerve terminal, whereas A2AR localizes in the postsynaptic muscle and in the axon and nerve terminal. Here, we use Western blotting to investigate the presence of A2BR and A3R receptors in striated muscle and immunohistochemistry to localize them in the three cells of the adult neuromuscular synapse. The data show that A2BR and A3R receptors are present in the nerve terminal and muscle cells at the NMJs. Neither A2BR nor A3R receptors are localized in the Schwann cells. Thus, the four subtypes of adenosine receptors are present in the motor endings. The presence of these receptors in the neuromuscular synapse allows the receptors to be involved in the modulation of transmitter release
Adenosine A1 and A2A receptor-mediated modulation of acetylcholine release in the mice neuromuscular junction
10.1111/ejn.1222
Presynaptic membrane receptors in acetylcholine release modulation on neuromuscular synapse
10.1002/jnr.23346Over the past few years, we have studied, in the mammalian neuromuscular junction (NMJ), the local involvement in transmitter release of the presynaptic muscarinic ACh autoreceptors (mAChRs), purinergic adenosine autoreceptors (P1Rs), and trophic factor receptors (TFRs; for neurotrophins and trophic cytokines) during development and in the adult. At any given moment, the way in which a synapse works is largely the logical outcome of the confluence of these (and other) metabotropic signalling pathways on intracellular kinases, which phosphorylate protein targets and materialize adaptive changes. We propose an integrated interpretation of the complementary function of these receptors in the adult NMJ. The activity of a given receptor group can modulate a given combination of spontaneous, evoked, and activity-dependent release characteristics. For instance, P1Rs can conserve resources by limiting spontaneous quantal leak of ACh (an A1R action) and protect synapse function, because stimulation with adenosine reduces the magnitude of depression during repetitive activity. The overall outcome of the mAChRs seems to contribute to upkeep of spontaneous quantal output of ACh, save synapse function by decreasing the extent of evoked release (mainly an M2 action), and reduce depression. We have also identified several links among P1Rs, mAChRs, and TFRs. We found a close dependence between mAChR and some TFRs and observed that the muscarinic group has to operate correctly if the tropomyosin-related kinase B receptor (trkB) is also to operate correctly, and vice versa. Likewise, the functional integrity of mAChRs depends on P1Rs operating normally