428 research outputs found
Studies of the Giant Dipole Resonance in Al, Ca, Fe, Ni and Pb with high energy-resolution inelastic proton scattering under 0
A survey of the fine structure of the Isovector Giant Dipole Resonance
(IVGDR) was performed, using the recently commissioned zero-degree facility of
the K600 magnetic spectrometer at iThemba LABS. Inelastic proton scattering at
an incident energy of 200 MeV was measured on Al, Ca, Fe,
Ni and Pb. A high energy resolution (
40 keV FWHM) could be achieved after utilising faint-beam and
dispersion-matching techniques. Considerable fine structure is observed in the
energy region of the IVGDR and characteristic energy scales are extracted from
the experimental data by means of a wavelet analysis. The comparison with
Quasiparticle-Phonon Model (QPM) calculations provides insight into the
relevance of different giant resonance decay mechanisms. Photoabsorption cross
sections derived from the data assuming dominance of relativistic Coulomb
excitation are in fair agreement with previous work using real photons.Comment: 15 pages, 15 figure
Pygmy dipole resonance in 208Pb
Scattering of protons of several hundred MeV is a promising new spectroscopic
tool for the study of electric dipole strength in nuclei. A case study of 208Pb
shows that at very forward angles J^pi = 1- states are strongly populated via
Coulomb excitation. A separation from nuclear excitation of other modes is
achieved by a multipole decomposition analysis of the experimental cross
sections based on theoretical angular distributions calculated within the
quasiparticle-phonon model. The B(E1) transition strength distribution is
extracted for excitation energies up to 9 MeV, i.e., in the region of the
so-called pygmy dipole resonance (PDR). The Coulomb-nuclear interference shows
sensitivity to the underlying structure of the E1 transitions, which allows for
the first time an experimental extraction of the electromagnetic transition
strength and the energy centroid of the PDR.Comment: submitted to Phys. Rev.
Low-energy electric dipole response in 120Sn
The electric dipole strength in 120Sn has been extracted from proton
inelastic scattering experiments at E_p = 295 MeV and at forward angles
including 0 degree. Below neutron threshoild it differs from the results of a
120Sn(gamma,gamma') experiment and peaks at an excitation energy of 8.3 MeV.
The total strength corresponds to 2.3(2)% of the energy-weighted sum rule and
is more than three times larger than what is observed with the (gamma,gamma')
reaction. This implies a strong fragmentation of the E1 strength and/or small
ground state branching ratios of the excited 1- states.Comment: 7 pages, 6 figure
Very late-onset neuromyelitis optica spectrum disorder beyond the age of 75
Aquaporin-4 antibody (AQP4-Ab)-positive neuromyelitis optica spectrum disorder (NMOSD) is a rare but often severe autoimmune disease with median onset around 40Â years of age. We report characteristics of three very-late-onset NMOSD (including complete NMO) patients >75Â years of age, in whom this diagnosis initially seemed unlikely because of their age and age-associated concomitant diseases, and briefly review the literature. All three patients, aged 79, 82 and 88 years, presented with a spinal cord syndrome as the first clinical manifestation of AQP4-Ab-positive NMOSD. They all had severe relapses unless immunosuppressive therapy was initiated, and one untreated patient died of a fatal NMOSD course. Two patients developed side effects of immunosuppression. We conclude that a first manifestation of NMOSD should be considered even in patients beyond the age of 75 years with a compatible syndrome, especially longitudinally extensive myelitis. Early diagnosis and treatment are feasible and highly relevant. Special attention is warranted in the elderly to recognize adverse effects of immunosuppressive therapies as early as possible
Complete electric dipole response and the neutron skin in 208Pb
A benchmark experiment on 208Pb shows that polarized proton inelastic
scattering at very forward angles including 0{\deg} is a powerful tool for
high-resolution studies of electric dipole (E1) and spin magnetic dipole (M1)
modes in nuclei over a broad excitation energy range to test up-to-date nuclear
models. The extracted E1 polarizability leads to a neutron skin thickness
r_skin = 0.156+0.025-0.021 fm in 208Pb derived within a mean-field model [Phys.
Rev. C 81, 051303 (2010)], thereby constraining the symmetry energy and its
density dependence, relevant to the description of neutron stars.Comment: 5 pages, 5 figures, revised mansucrip
Dipole polarizability of 120Sn and nuclear energy density functionals
The electric dipole strength distribution in 120Sn between 5 and 22 MeV has
been determined at RCNP Osaka from a polarization transfer analysis of proton
inelastic scattering at E_0 = 295 MeV and forward angles including 0{\deg}.
Combined with photoabsorption data an electric dipole polarizability
\alpha_D(120Sn) = 8.93(36) fm^3 is extracted. The dipole polarizability as
isovector observable par excellence carries direct information on the nuclear
symmetry energy and its density dependence. The correlation of the new value
with the well established \alpha_D(208Pb) serves as a test of its prediction by
nuclear energy density functionals (EDFs). Models based on modern Skyrme
interactions describe the data fairly well while most calculations based on
relativistic Hamiltonians cannot.Comment: 6 pages, 4 figure
In vitro and in vivo effects of Pelargonium sidoides DC. root extract EPs® 7630 and selected constituents against SARS-CoV-2 B.1, Delta AY.4/AY.117 and Omicron BA.2
The occurrence of immune-evasive SARS-CoV-2 strains emphasizes the importance to search for broad-acting antiviral compounds. Our previous in vitro study showed that Pelargonium sidoides DC. root extract EPs® 7630 has combined antiviral and immunomodulatory properties in SARS-CoV-2-infected human lung cells. Here we assessed in vivo effects of EPs® 7630 in SARS-CoV-2-infected hamsters, and investigated properties of EPs® 7630 and its functionally relevant constituents in context of phenotypically distinct SARS-CoV-2 variants. We show that EPs® 7630 reduced viral load early in the course of infection and displayed significant immunomodulatory properties positively modulating disease progression in hamsters. In addition, we find that EPs® 7630 differentially inhibits SARS-CoV-2 variants in nasal and bronchial human airway epithelial cells. Antiviral effects were more pronounced against Omicron BA.2 compared to B.1 and Delta, the latter two preferring TMPRSS2-mediated fusion with the plasma membrane for cell entry instead of receptor-mediated low pH-dependent endocytosis. By using SARS-CoV-2 Spike VSV-based pseudo particles (VSVpp), we confirm higher EPs® 7630 activity against Omicron Spike-VSVpp, which seems independent of the serine protease TMPRSS2, suggesting that EPs® 7630 targets endosomal entry. We identify at least two molecular constituents of EPs® 7630, i.e., (−)-epigallocatechin and taxifolin with antiviral effects on SARS-CoV-2 replication and cell entry. In summary, our study shows that EPs® 7630 ameliorates disease outcome in SARS-CoV-2-infected hamsters and has enhanced activity against Omicron, apparently by limiting late endosomal SARS-CoV-2 entry
Cross-protection against European swine influenza viruses in the context of infection immunity against the 2009 pandemic H1N1 virus : studies in the pig model of influenza
Pigs are natural hosts for the same influenza virus subtypes as humans and are a valuable model for cross-protection studies with influenza. In this study, we have used the pig model to examine the extent of virological protection between a) the 2009 pandemic H1N1 (pH1N1) virus and three different European H1 swine influenza virus (SIV) lineages, and b) these H1 viruses and a European H3N2 SIV. Pigs were inoculated intranasally with representative strains of each virus lineage with 6- and 17-week intervals between H1 inoculations and between H1 and H3 inoculations, respectively. Virus titers in nasal swabs and/or tissues of the respiratory tract were determined after each inoculation. There was substantial though differing cross-protection between pH1N1 and other H1 viruses, which was directly correlated with the relatedness in the viral hemagglutinin (HA) and neuraminidase (NA) proteins. Cross-protection against H3N2 was almost complete in pigs with immunity against H1N2, but was weak in H1N1/pH1N1-immune pigs. In conclusion, infection with a live, wild type influenza virus may offer substantial cross-lineage protection against viruses of the same HA and/or NA subtype. True heterosubtypic protection, in contrast, appears to be minimal in natural influenza virus hosts. We discuss our findings in the light of the zoonotic and pandemic risks of SIVs
Cerebrospinal Fluid B Cells Correlate with Early Brain Inflammation in Multiple Sclerosis
Background: There is accumulating evidence from immunological, pathological and therapeutic studies that B cells are key components in the pathophysiology of multiple sclerosis (MS). Methodology/Principal Findings: In this prospective study we have for the first time investigated the differences in the inflammatory response between relapsing and progressive MS by comparing cerebrospinal fluid (CSF) cell profiles from patients at the onset of the disease (clinically isolated syndrome, CIS), relapsing-remitting (RR) and chronic progressive (CP) MS by flow cytometry. As controls we have used patients with other neurological diseases. We have found a statistically significant accumulation of CSF mature B cells (CD19+CD1382) and plasma blasts (CD19+CD138+) in CIS and RRMS. Both B cell populations were, however, not significantly increased in CPMS. Further, this accumulation of B cells correlated with acute brain inflammation measured by magnetic resonance imaging and with inflammatory CSF parameters such as the number of CSF leukocytes, intrathecal immunoglobulin M and G synthesis and intrathecal production of matri
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