39 research outputs found
Chiral Symmetry and the Nucleon Structure Functions
The isospin asymmetry of the sea quark distribution as well as the
unexpectedly small quark spin fraction of the nucleon are two outstanding
discoveries recently made in the physics of deep-inelastic structure functions.
We evaluate here the corresponding quark distribution functions within the
framework of the chiral quark soliton model, which is an effective quark model
of baryons maximally incorporating the most important feature of low energy
QCD, i.e. the chiral symmetry and its spontaneous breakdown. It is shown that
the model can explain qualitative features of the above-mentioned nucleon
structure functions within a single framework, thereby disclosing the
importance of chiral symmetry in the physics of high energy deep-inelastic
scatterings.Comment: 20pages, LaTex, 5 Postscript figures A numerical error of the
original version was corrected. The discussion on the regularization
dependence of distribution functions has been added. A comparison with the
low energy-scale parametrization of Gloeck, Reya and Vogt has been mad
The Crystal Ball Data Acquisition System
The data acquisition system for the Crystal Ball project at SLAC is described. A PDP-11/t55 using RSX-11M connected to the SLAC Triplex is the basis of the system. A "physics pipeline" allows physicists to write their own equipment-monitoring or physics tasks which require event sampling. As well, an interactive analysis package (MULTI) is in the pipeline. Histogram collection and display on the PDP are implemented using the Triplex histogramming package. Various interactive event displays are also implemented
Chiral Symmetry and the Nucleon Spin Structure Functions
We carry out a systematic investigation of twist-two spin dependent structure
functions of the nucleon within the framework of the chiral quark soliton model
(CQSM) by paying special attention to the role of chiral symmetry of QCD. The
importance of chiral symmetry is illustrated through the good reproduction of
the recent SLAC data for the neutron spin structure function .
We also observe substantial difference between the predictions of the
longitudinally polarized distribution functions and those of the transversity
distribution functions. That the chiral symmetry may be responsible for this
difference is seen in the isospin dependence of the corresponding first
moments, i.e. the axial and tensor charges. The CQSM predicts for the ratio of the isoscalar to isovector axial
charges, while for the ratio of the
isoscalar to isovector tensor charges, which should be compared with the
prediction of the
constituent quark model or of the naive MIT bag model without proper account of
chiral symmetry. Another prominent prediction of the CQSM is the opposite
polarization of the and antiquarks, thereby indicating the
SU(2) asymmetric sea quark (spin) polarization in the nucleon.Comment: 46pages, LaTeX, 16 Postscript figure
SARS-CoV-2-mediated dysregulation of metabolism and autophagy uncovers host-targeting antivirals
Viruses manipulate cellular metabolism and macromolecule recycling processes like autophagy. Dysregulated metabolism might lead to excessive inflammatory and autoimmune responses as observed in severe and long COVID-19 patients. Here we show that SARS-CoV-2 modulates cellular metabolism and reduces autophagy. Accordingly, compound-driven induction of autophagy limits SARS-CoV-2 propagation. In detail, SARS-CoV-2-infected cells show accumulation of key metabolites, activation of autophagy inhibitors (AKT1, SKP2) and reduction of proteins responsible for autophagy initiation (AMPK, TSC2, ULK1), membrane nucleation, and phagophore formation (BECN1, VPS34, ATG14), as well as autophagosome-lysosome fusion (BECN1, ATG14 oligomers). Consequently, phagophore-incorporated autophagy markers LC3B-II and P62 accumulate, which we confirm in a hamster model and lung samples of COVID-19 patients. Single-nucleus and single-cell sequencing of patient-derived lung and mucosal samples show differential transcriptional regulation of autophagy and immune genes depending on cell type, disease duration, and SARS-CoV-2 replication levels. Targeting of autophagic pathways by exogenous administration of the polyamines spermidine and spermine, the selective AKT1 inhibitor MK-2206, and the BECN1-stabilizing anthelmintic drug niclosamide inhibit SARS-CoV-2 propagation in vitro with IC(50) values of 136.7, 7.67, 0.11, and 0.13 μM, respectively. Autophagy-inducing compounds reduce SARS-CoV-2 propagation in primary human lung cells and intestinal organoids emphasizing their potential as treatment options against COVID-19
Distinct tissue niches direct lung immunopathology via CCL18 and CCL21 in severe COVID-19
Prolonged lung pathology has been associated with COVID-19, yet the cellular and molecular mechanisms behind this chronic inflammatory disease are poorly understood. In this study, we combine advanced imaging and spatial transcriptomics to shed light on the local immune response in severe COVID-19. We show that activated adventitial niches are crucial microenvironments contributing to the orchestration of prolonged lung immunopathology. Up-regulation of the chemokines CCL21 and CCL18 associates to endothelial-to-mesenchymal transition and tissue fibrosis within these niches. CCL21 over-expression additionally links to the local accumulation of T cells expressing the cognate receptor CCR7. These T cells are imprinted with an exhausted phenotype and form lymphoid aggregates that can organize in ectopic lymphoid structures. Our work proposes immune-stromal interaction mechanisms promoting a self-sustained and non-resolving local immune response that extends beyond active viral infection and perpetuates tissue remodeling
β and γ bands in N = 88 , 90, and 92 isotones investigated with a five-dimensional collective Hamiltonian based on covariant density functional theory : vibrations, shape coexistence, and superdeformation
CITATION: Majola, S. N. T. et al. 2019. β and γ bands in N=88, 90, and 92 isotones investigated with a five-dimensional collective Hamiltonian based on covariant density functional theory: Vibrations, shape coexistence, and superdeformation. Physical Review C, 100(4). doi:10.1103/PhysRevC.100.044324.The original publication is available at https://journals.aps.org/prc/A comprehensive systematic study is made for the collective β and γ bands in even-even isotopes with neutron numbers N = 88 to 92 and proton numbers Z = 62 (Sm) to 70 (Yb). Data, including excitation energies,
B(E0) and B(E2) values, and branching ratios from previously published experiments are collated with new
data presented for the first time in this study. The experimental data are compared to calculations using a
five-dimensional collective Hamiltonian (5DCH) based on the covariant density functional theory (CDFT). A
realistic potential in the quadrupole shape parameters V (β,γ ) is determined from potential energy surfaces
(PES) calculated using the CDFT. The parameters of the 5DCH are fixed and contained within the CDFT.
Overall, a satisfactory agreement is found between the data and the calculations. In line with the energy
staggering S(I) of the levels in the 2γ
+ bands, the potential energy surfaces of the CDFT calculations indicate
γ -soft shapes in the N = 88 nuclides, which become γ rigid for N = 90 and N = 92. The nature of the 02
+
bands changes with atomic number. In the isotopes of Sm to Dy, they can be understood as β vibrations, but in
the Er and Yb isotopes the 02
+ bands have wave functions with large components in a triaxial superdeformed
minimum. In the vicinity of 152Sm, the present calculations predict a soft potential in the β direction but do not
find two coexisting minima. This is reminiscent of 152Sm exhibiting an X(5) behavior. The model also predicts
that the 03
+ bands are of two-phonon nature, having an energy twice that of the 02
+ band. This is in contradiction
with the data and implies that other excitation modes must be invoked to explain their origin.https://journals.aps.org/prc/abstract/10.1103/PhysRevC.100.044324Publisher’s versio
The impact of the Hyde Park-Kenwood Urban Renewal Plan on municipal finances in Chicago /
Cover title.Mode of access: Internet