129 research outputs found
Presurgical diagnosis of diffuse gliomas in adults:Post-WHO 2021 practical perspectives from radiologists in neuro-oncology units
The 2021 World Health Organization classification of CNS tumours was greeted with enthusiasm as well as an initial potential overwhelm. However, with time and experience, our understanding of its key aspects has notably improved. Using our collective expertise gained in neuro-oncology units in hospitals in different countries, we have compiled a practical guide for radiologists that clarifies the classification criteria for diffuse gliomas in adults. Its format is clear and concise to facilitate its incorporation into everyday clinical practice. The document includes a historical overview of the classifications and highlights the most important recent additions. It describes the main types in detail with an emphasis on their appearance on imaging. The authors also address the most debated issues in recent years. It will better prepare radiologists to conduct accurate presurgical diagnoses and collaborate effectively in clinical decision making, thus impacting decisions on treatment, prognosis, and overall patient care.</p
Presurgical diagnosis of diffuse gliomas in adults:Post-WHO 2021 practical perspectives from radiologists in neuro-oncology units
The 2021 World Health Organization classification of CNS tumours was greeted with enthusiasm as well as an initial potential overwhelm. However, with time and experience, our understanding of its key aspects has notably improved. Using our collective expertise gained in neuro-oncology units in hospitals in different countries, we have compiled a practical guide for radiologists that clarifies the classification criteria for diffuse gliomas in adults. Its format is clear and concise to facilitate its incorporation into everyday clinical practice. The document includes a historical overview of the classifications and highlights the most important recent additions. It describes the main types in detail with an emphasis on their appearance on imaging. The authors also address the most debated issues in recent years. It will better prepare radiologists to conduct accurate presurgical diagnoses and collaborate effectively in clinical decision making, thus impacting decisions on treatment, prognosis, and overall patient care.</p
Search for Light Gauge Bosons of the Dark Sector at the Mainz Microtron
A new exclusion limit for the electromagnetic production of a light U(1)
gauge boson {\gamma}' decaying to e^+e^- was determined by the A1 Collaboration
at the Mainz Microtron. Such light gauge bosons appear in several extensions of
the standard model and are also discussed as candidates for the interaction of
dark matter with standard model matter. In electron scattering from a heavy
nucleus, the existing limits for a narrow state coupling to e^+e^- were reduced
by nearly an order of magnitude in the range of the lepton pair mass of 210
MeV/c^2 < m_e^+e^- < 300 MeV/c^2. This experiment demonstrates the potential of
high current and high resolution fixed target experiments for the search for
physics beyond the standard model.Comment: 4 pages, 7 figure
Recoil polarization and beam-recoil double polarization measurement of \eta electroproduction on the proton in the region of the S_{11}(1535) resonance
The beam-recoil double polarization P_{x'}^h and P_{z'}^h and the recoil
polarization P_{y'} were measured for the first time for the
p(\vec{e},e'\vec{p})\eta reaction at a four-momentum transfer of Q^2=0.1
GeV^2/c^2 and a center of mass production angle of \theta = 120^\circ at MAMI
C. With a center of mass energy range of 1500 MeV < W < 1550 MeV the region of
the S_{11}(1535) and D_{13}(1520) resonance was covered. The results are
discussed in the framework of a phenomenological isobar model (Eta-MAID). While
P_{x'}^h and P_{z'}^h are in good agreement with the model, P_{y'} shows a
significant deviation, consistent with existing photoproduction data on the
polarized-target asymmetry.Comment: 4 pages, 1 figur
The electric and magnetic form factors of the proton
The paper describes a precise measurement of electron scattering off the
proton at momentum transfers of \ GeV. The
average point-to-point error of the cross sections in this experiment is
0.37%. These data are used for a coherent new analysis together with all world
data of unpolarized and polarized electron scattering from the very smallest to
the highest momentum transfers so far measured. The extracted electric and
magnetic form factors provide new insight into their exact shape, deviating
from the classical dipole form, and of structure on top of this gross shape.
The data reaching very low values are used for a new determination of the
electric and magnetic radii. An empirical determination of the
Two-Photon-Exchange (TPE) correction is presented. The implications of this
correction on the radii and the question of a directly visible signal of the
pion cloud are addressed.Comment: 38 pages, 20 figures. Updated data files. PRC versio
Reply to Comment on "High-Precision Determination of the Electric and Magnetic Form Factors of the Proton"
In arXiv:1108.3058v1 [nucl-ex], Arrington criticizes the Coulomb corrections
we applied in the analysis of high precision form factor data (see
Phys.Rev.Lett.105:242001, 2010, arXiv:1007.5076v3 [nucl-ex]). We show, by
comparing different calculations cited in the Comment, that the criticism of
the Comment neglects the large uncertainty of "more modern" TPE corrections.
This uncertainty has also been seen in recent polarized measurements. We rerun
our analysis using one of these calculations. The results show that the Comment
exaggerates the quantitative effect at small Q^2.Comment: 1 page, 2 figure, To appear as a Reply Comment in Physical Review
Letter
High-precision determination of the electric and magnetic form factors of the proton
New precise results of a measurement of the elastic electron-proton
scattering cross section performed at the Mainz Microtron MAMI are presented.
About 1400 cross sections were measured with negative four-momentum transfers
squared up to Q^2=1 (GeV/c)^2 with statistical errors below 0.2%. The electric
and magnetic form factors of the proton were extracted by fits of a large
variety of form factor models directly to the cross sections. The form factors
show some features at the scale of the pion cloud. The charge and magnetic
radii are determined to be r_E=0.879(5)(stat.)(4)(syst.)(2)(model)(4)(group) fm
and r_M=0.777(13)(stat.)(9)(syst.)(5)(model)(2)(group) fm.Comment: 5 pages, 2 figures, published in Phys. Rev. Lett. v3: added
references, updated text, color figure
A Large-Scale FPGA-Based Trigger and Dead-Time Free DAQ System for the Kaos Spectrometer at MAMI
The Kaos spectrometer is maintained by the A1 collaboration at the Mainz
Microtron MAMI with a focus on the study of (e,e'K^+) coincidence reactions.
For its electron-arm two vertical planes of fiber arrays, each comprising
approximately 10 000 fibers, are operated close to zero degree scattering angle
and in close proximity to the electron beam. A nearly dead-time free DAQ system
to acquire timing and tracking information has been installed for this
spectrometer arm. The signals of 144 multi-anode photomultipliers are collected
by 96-channel front-end boards, digitized by double-threshold discriminators
and the signal time is picked up by state-of-the-art F1 time-to-digital
converter chips. In order to minimize background rates a sophisticated trigger
logic was implemented in newly developed Vuprom modules. The trigger performs
noise suppression, signal cluster finding, particle tracking, and coincidence
timing, and can be expanded for kinematical matching (e'K^+) coincidences. The
full system was designed to process more than 4 000 read-out channels and to
cope with the high electron flux in the spectrometer and the high count rate
requirement of the detectors. It was successfully in-beam tested at MAMI in
2009.Comment: Contributed to 17th IEEE Real Time Conference (RT10), Lisbon, 24-28
May 201
Nucleolin reorganization and nucleolar stress in Purkinje cells of mutant PCD mice
The Purkinje cell (PC) degeneration (pcd) mouse harbors a mutation in Agtpbp1 gene that encodes for the cytosolic carboxypeptidase, CCP1. The mutation causes degeneration and death of PCs during the postnatal life, resulting in clinical and pathological manifestation of cerebellar ataxia. Monogenic biallelic damaging variants in the Agtpbp1 gene cause infantile-onset neurodegeneration and cerebellar atrophy, linking loss of functional CCP1 with human neurodegeneration. Although CCP1 plays a key role in the regulation of tubulin stabilization, its loss of function in PCs leads to a severe nuclear phenotype with heterochromatinization and accumulation of DNA damage. Therefore, the pcd mice provides a useful neuronal model to investigate nuclear mechanisms involved in neurodegeneration, particularly the nucleolar stress. In this study, we demonstrated that the Agtpbp1 gene mutation induces a p53-dependent nucleolar stress response in PCs, which is characterized by nucleolar fragmentation, nucleoplasmic and cytoplasmic mislocalization of nucleolin, and dysfunction of both pre-rRNA processing and mRNA translation. RT-qPCR analysis revealed reduction of mature 18S rRNA, with a parallel increase of its intermediate 18S-5'-ETS precursor, that correlates with a reduced expression of Fbl mRNA, which encodes an essential factor for rRNA processing. Moreover, nucleolar alterations were accompanied by a reduction of PTEN mRNA and protein levels, which appears to be related to the chromosome instability and accumulation of DNA damage in degenerating PCs. Our results highlight the essential contribution of nucleolar stress to PC degeneration and also underscore the nucleoplasmic mislocalization of nucleolin as a potential indicator of neurodegenerative processes.Acknowledgements: The authors declare no conflict of interest. The authors wish to thank Raquel García-Ceballos for technical assistance. This work was supported by the following grants: “Instituto de Salud Carlos III” (CIBERNED, CB06/05/0037) and CIBERONC (CB16/12/00352), “Instituto de Investigación Valdecilla” (IDIVAL, Santander, Spain), FIS PI16/02137 from ISCIII and SAF2016-79668-R (MINECO, Spain), SA043U16 (UIC076) and SA030P17 (UIC217) from JCyL (Spain)
- …