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Träfflista för sökning "WFRF:(Blumer J) "

Sökning: WFRF:(Blumer J)

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1.
  • Adrich, P., et al. (författare)
  • Production of antihydrogen atoms by 6 keV antiprotons through a positronium cloud
  • 2023
  • Ingår i: European Physical Journal C. - : Springer Nature. - 1434-6044 .- 1434-6052. ; 83:11
  • Tidskriftsartikel (refereegranskat)abstract
    • We report on the first production of an antihydrogen beam by charge exchange of 6.1 keV antiprotons with a cloud of positronium in the GBAR experiment at CERN. The 100 keV antiproton beam delivered by the AD/ELENA facility was further decelerated with a pulsed drift tube. A 9 MeV electron beam from a linear accelerator produced a low energy positron beam. The positrons were accumulated in a set of two Penning-Malmberg traps. The positronium target cloud resulted from the conversion of the positrons extracted from the traps. The antiproton beam was steered onto this positronium cloud to produce the antiatoms. We observe an excess over background indicating antihydrogen production with a significance of 3-4 standard deviations.
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2.
  • Blumer, P., et al. (författare)
  • Positron accumulation in the GBAR experiment
  • 2022
  • Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 1040
  • Tidskriftsartikel (refereegranskat)abstract
    • We present a description of the GBAR positron (e+) trapping apparatus, which consists of a three stage Buffer Gas Trap (BGT) followed by a High Field Penning Trap (HFT), and discuss its performance. The overall goal of the GBAR experiment is to measure the acceleration of the neutral antihydrogen (H¯) atom in the terrestrial gravitational field by neutralising a positive antihydrogen ion (H¯+), which has been cooled to a low temperature, and observing the subsequent H¯ annihilation following free fall. To produce one H¯+ ion, about 1010 positrons, efficiently converted into positronium (Ps), together with about 107 antiprotons (p¯), are required. The positrons, produced from an electron linac-based system, are accumulated first in the BGT whereafter they are stacked in the ultra-high vacuum HFT, where we have been able to trap 1.4(2) × 109 positrons in 1100 s.
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3.
  • Chacko, L. Johnson, et al. (författare)
  • Role of BDNF and neurotrophic receptors in human inner ear development
  • 2017
  • Ingår i: Cell and Tissue Research. - : SPRINGER. - 0302-766X .- 1432-0878. ; 370:3, s. 347-363
  • Tidskriftsartikel (refereegranskat)abstract
    • The expression patterns of the neurotrophin, brain-derived neurotrophic factor, BDNF, and the neurotrophic receptors-p75NTR and Trk receptors-in the developing human fetal inner ear between the gestational weeks (GW) 9 to 12 are examined via in situ hybridization and immunohistochemistry. BDNF mRNA expression was highest in the cochlea at GW 9 but declined in the course of development. In contrast to embryonic murine specimens, a decline in BDNF expression from the apical to the basal turn of the cochlea could not be observed. p75NTR immunostaining was most prominent in the nerve fibers that penetrate into the sensory epithelia of the cochlea, the urticule and the saccule as gestational age progresses. TrkB and TrkC expression intensified towards GW 12, at which point the BDNF mRNA localization was at its lowest. TrkA expression was limited to fiber subpopulations of the facial nerve at GW 10. In the adult human inner ear, we observed BDNF mRNA expression in the apical poles of the cochlear hair cells and supporting cells, while in the adult human utricle, the expression was localized in the vestibular hair cells. We demonstrate the highly specific staining patterns of BDNF mRNA and its putative receptors over a developmental period in which multiple hearing disorders are manifested. Our findings suggest that BDNF and neurotrophin receptors are important players during early human inner ear development. In particular, they seem to be important for the survival of the afferent sensory neurons.
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4.
  • Johnson Chacko, Lejo, et al. (författare)
  • Neurosensory Differentiation and Innervation Patterning in the Human Fetal Vestibular End Organs between the Gestational Weeks 8-12
  • 2016
  • Ingår i: Frontiers in Neuroanatomy. - : Frontiers Media SA. - 1662-5129. ; 10
  • Tidskriftsartikel (refereegranskat)abstract
    • Balance orientation depends on the precise operation of the vestibular end organs and the vestibular ganglion neurons. Previous research on the assemblage of the neuronal network in the developing fetal vestibular organ has been limited to data from animal models. Insights into the molecular expression profiles and signaling moieties involved in embryological development of the human fetal inner ear have been limited. We present an investigation of the cells of the vestibular end organs with specific focus on the hair cell differentiation and innervation pattern using an uninterrupted series of unique specimens from gestational weeks 8-12. Nerve fibers positive for peripherin innervate the entire fetal crista and utricle. While in rodents only the peripheral regions of the cristae and the extra-striolar region of the statolithic organs are stained. At week 9, transcription factors PAX2 and PAX8 were observed in the hair cells whereas PAX6 was observed for the first time among the supporting cells of the cristae and the satellite glial cells of the vestibular ganglia. Glutamine synthetase, a regulator of the neurotransmitter glutamate, is strongly expressed among satellite glia cells, transitional zones of the utricle and supporting cells in the sensory epithelium. At gestational week 11, electron microscopic examination reveals bouton contacts at hair cells and first signs of the formation of a protocalyx at type I hair cells. Our study provides first-hand insight into the fetal development of the vestibular end organs as well as their pattern of innervation by means of immunohistochemical and EM techniques, with the aim of contributing toward our understanding of balance development.
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5.
  • Pechriggl, Elisabeth J, et al. (författare)
  • Development of the innervation of the human inner ear
  • 2015
  • Ingår i: Developmental Neurobiology. - : Wiley. - 1932-8451 .- 1932-846X. ; 75:7, s. 683-702
  • Tidskriftsartikel (refereegranskat)abstract
    • Studies on the formation of neuronal structures of the human cochlea are rare, presumptively, due to the difficult accessibility of specimens, so that most investigations are performed on mouse models. By means of immunohistochemical and transmission electron microscopic techniques, we investigated an uninterrupted series of unique specimens from gestational week 8 to week 12. We were able to demonstrate the presence of nerve fibers in the prosensory domain at gestational week 8, followed by afferent synaptogenesis at week 11. We identified PAX2 as an early marker for hair cell differentiation. Glutamine synthetase-positive peripheral glial cells occurred at the beginning of week 8. Transcription factor MAF B was used to demonstrate maturation of the spiral ganglion neurons. The early expression of tyrosine hydroxylase could be assessed. This study provides insights in the early assembly of the neural circuit and organization in humans.
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7.
  • Hermann-Kleiter, Natascha, et al. (författare)
  • Lasp1 misexpression influences chondrocyte differentiation in the vertebral column
  • 2009
  • Ingår i: International Journal of Developmental Biology. - : UPV/EHU Press. - 1696-3547 .- 0214-6282. ; 53:7, s. 983-991
  • Tidskriftsartikel (refereegranskat)abstract
    • The mouse mutant wavy tail Tg(Col1a1-lacZ)304ng was created through transgene insertion and exhibits defects of the vertebral column. Homozygous mutant animals have compressed tail vertebrae and wedge-shaped intervertebral discs, resulting in a meandering tail. Delayed closure of lumbar neural arches and lack of processus spinosi have been observed; these defects become most prominent during the transition from cartilage to bone. The spina bifida was resistant to folic acid treatment, while retinoic acid administration caused severe skeletal defects in the mutant, but none in wild type control animals. The transgene integrated at chromosome 11 band D, in an area of high gene density. The insertion site was located between the transcription start sites of the RpI23 and Lasp1 genes. LASP1 (an actin binding protein involved in cell migration and survival) was found to be produced in resting and hypertrophic chondrocytes in the vertebrae. In mutant vertebrae, temporal and spatial misexpression of Lasp1 was observed, indicating that alterations in Lasp1 transcription are most likely responsible for the observed phenotype. These data reveal a yet unappreciated role of Lasp1 in chondrocyte differentiation during cartilage to bone transition.
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  • Resultat 1-10 av 10

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