78 research outputs found
Instabilities of a hot expanded nuclear droplet
The stability of hot expanded nuclear droplets against small bulk and surface
oscillations is examined and possible consequences for multifragmentation are
discussed.Comment: LaTeX (uses epsfig.sty), 6 pages with 6 eps figures inside text. Talk
given at XXVII International Workshop on Gross Properties of Nuclei and
Nuclear Excitations, "MULTIFRAGMENTATION", Hirschegg, January 17--23, 199
Stability and instability of a hot and dilute nuclear droplet
The diabatic approach to collective nuclear motion is reformulated in the
local-density approximation in order to treat the normal modes of a spherical
nuclear droplet analytically. In a first application the adiabatic isoscalar
modes are studied and results for the eigenvalues of compressional (bulk) and
pure surface modes are presented as function of density and temperature inside
the droplet, as well as for different mass numbers and for soft and stiff
equations of state. We find that the region of bulk instabilities (spinodal
regime) is substantially smaller for nuclear droplets than for infinite nuclear
matter. For small densities below 30% of normal nuclear matter density and for
temperatures below 5 MeV all relevant bulk modes become unstable with the same
growth rates. The surface modes have a larger spinodal region, reaching out to
densities and temperatures way beyond the spinodal line for bulk instabilities.
Essential experimental features of multifragmentation, like fragmentation
temperatures and fragment-mass distributions (in particular the power-law
behavior) are consistent with the instability properties of an expanding
nuclear droplet, and hence with a dynamical fragmentation process within the
spinodal regime of bulk and surface modes (spinodal decomposition).Comment: 17 pages, 11 figures, LaTeX2e, EPJA style (included
eta-meson photoproduction off protons and deuterons
We present a unitary and gauge-invariant model with coupled channels, which
provides a consistent description of pion photoproduction off nucleons in the
E channel and eta-meson photoproduction off protons and deuterons. An
effective field theory with hadrons and photons is constructed, which includes
non-resonant Born terms as well as the S(1535) and S(1650) baryon
resonances. Due to the coupling between the channels, the production of
eta-mesons is strongly affected by the S(1650) although its direct
coupling to the N channel is negligible. The rho- and omega-meson
exchange terms are important for achieving a consistent description of both
pion- and photon-induced reactions.Comment: 11 pages Latex, 4 Postscript Figure
Directed Flow of Baryons in Heavy-Ion Collisions
The collective motion of nucleons from high-energy heavy-ion collisions is
analyzed within a relativistic two-fluid model for different equations of state
(EoS). As function of beam energy the theoretical slope parameter F_y of the
differential directed flow is in good agreement with experimental data, when
calculated for the QCD-consistent EoS described by the statistical mixed-phase
model. Within this model, which takes the deconfinement phase transition into
account, the excitation function of the directed flow turns out to be a
smooth function in the whole range from SIS till SPS energies. This function is
close to that for pure hadronic EoS and exhibits no minimum predicted earlier
for a two-phase bag-model EoS. Attention is also called to a possible formation
of nucleon antiflow (F_y < 0) at energies of the order of 100 A GeV.Comment: 7 pages, 5 figure
Global analysis of RNA-binding protein dynamics by comparative and enhanced RNA interactome capture
Interactions between RNA-binding proteins (RBPs) and RNAs are critical to cell biology. However, methods to comprehensively and quantitatively assess these interactions within cells were lacking. RNA interactome capture (RIC) uses in vivo UV crosslinking, oligo(dT) capture, and proteomics to identify RNA-binding proteomes. Recent advances have empowered RIC to quantify RBP responses to biological cues such as metabolic imbalance or virus infection. Enhanced RIC exploits the stronger binding of locked nucleic acid (LNA)-containing oligo(dT) probes to poly(A) tails to maximize RNA capture selectivity and efficiency, profoundly improving signal-to-noise ratios. The subsequent analytical use of SILAC and TMT proteomic approaches, together with high-sensitivity sample preparation and tailored statistical data analysis, substantially improves RICâs quantitative accuracy and reproducibility. This optimized approach is an extension of the original RIC protocol. It takes 3 d plus 2 weeks for proteomics and data analysis and will enable the study of RBP dynamics under different physiological and pathological conditions
Frequent ZNF217 mutations lead to transcriptional deregulation of interferon signal transduction via altered chromatin accessibility in B cell lymphoma
Recent exome-wide studies discovered frequent somatic mutations in the epigenetic modifier ZNF217 in primary mediastinal B cell lymphoma (PMBCL) and related disorders. As functional consequences of ZNF217 alterations remain unknown, we comprehensively evaluated their impact in PMBCL. Targeted sequencing identified genetic lesions affecting ZNF217 in 33% of 157 PMBCL patients. Subsequent gene expression profiling (nâ=â120) revealed changes in cytokine and interferon signal transduction in ZNF217-aberrant PMBCL cases. In vitro, knockout of ZNF217 led to changes in chromatin accessibility interfering with binding motifs for crucial lymphoma-associated transcription factors. This led to disturbed expression of interferon-responsive and inflammation-associated genes, altered cell behavior, and aberrant differentiation. Mass spectrometry demonstrates that ZNF217 acts within a histone modifier complex containing LSD1, CoREST and HDAC and interferes with H3K4 methylation and H3K27 acetylation. Concluding, our data suggest non-catalytic activity of ZNF217, which directs histone modifier complex function and controls B cell differentiation-associated patterns of chromatin structure
A prenylated dsRNA sensor protects against severe COVID-19
Inherited genetic factors can influence the severity of COVID-19, but the molecular explanation underpinning a genetic association is often unclear. Intracellular antiviral defenses can inhibit the replication of viruses and reduce disease severity. To better understand the antiviral defenses relevant to COVID-19, we used interferon-stimulated gene (ISG) expression screening to reveal that OAS1, through RNase L, potently inhibits SARS-CoV-2. We show that a common splice-acceptor SNP (Rs10774671) governs whether people express prenylated OAS1 isoforms that are membrane-associated and sense specific regions of SARS-CoV-2 RNAs, or only express cytosolic, nonprenylated OAS1 that does not efficiently detect SARS-CoV-2. Importantly, in hospitalized patients, expression of prenylated OAS1 was associated with protection from severe COVID-19, suggesting this antiviral defense is a major component of a protective antiviral response
A prenylated dsRNA sensor protects against severe COVID-19
Inherited genetic factors can influence the severity of COVID-19, but the molecular explanation underpinning a genetic association is often unclear. Intracellular antiviral defenses can inhibit the replication of viruses and reduce disease severity. To better understand the antiviral defenses relevant to COVID-19, we used interferon-stimulated gene (ISG) expression screening to reveal that OAS1, through RNase L, potently inhibits SARS-CoV-2. We show that a common splice-acceptor SNP (Rs10774671) governs whether people express prenylated OAS1 isoforms that are membrane-associated and sense specific regions of SARS-CoV-2 RNAs, or only express cytosolic, nonprenylated OAS1 that does not efficiently detect SARS-CoV-2. Importantly, in hospitalized patients, expression of prenylated OAS1 was associated with protection from severe COVID-19, suggesting this antiviral defense is a major component of a protective antiviral response
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