2,326 research outputs found
Mechanismen molekularer Erkennung: Charakterisierung der molekularen Details der Wechselwirkungen des herpesviralen Tip-Proteins mit SH3-DomÀnen
A schematic model for fragmentation and phase transition in nuclear collisions
We develop here a simple yet versatile model for nuclear fragmentation in
heavy ion collisions. The model allows us to calculate thermodynamic properties
such as phase transitions as well as the distribution of fragments at
disassembly. In spite of its simplicity the model gives very good fit to recent
data taken at the Michigan National Superconducting Cyclotron Laboratory. The
model is an extension of a lattice gas model which itself has strong overlaps
with percolation models which have been used in the past to compare with
nuclear fragmentation data.Comment: 12 pages (RevTex), 4 figures (uuencoded ps file), To appear in Phys.
Lett.
Lattice gas model for fragmentation: From Argon on Scandium to Gold on Gold
The recent fragmentation data for central collisions of Gold on Gold are even
qualitatively different from those for central collisions of Argon on Scandium.
The latter can be fitted with a lattice gas model calculation. Effort is made
to understand why the model fails for Gold on Gold. The calculation suggests
that the large Coulomb interaction which is operative for the larger system is
responsible for this discrepancy. This is demonstrated by mapping the lattice
gas model to a molecular dynamics calculation for disassembly. This mapping is
quite faithful for Argon on Scandium but deviates strongly for Gold on Gold.
The molecular dynamics calculation for disassembly reproduces the
characteristics of the fragmentation data for both Gold on Gold and Argon on
Scandium.Comment: 13 pages, Revtex, 8 figures in ps files, submitted to Phys. Rev.
Hard X-ray Morphological and Spectral Studies of The Galactic Center Molecular Cloud Sgr B2: Constraining Past Sgr A* Flaring Activity
Galactic Center (GC) molecular cloud Sgr B2 is the best manifestation of an
X-ray reflection nebula (XRN) reprocessing a past giant outburst from the
supermassive black hole Sgr A*. Alternatively, Sgr B2 could be illuminated by
low-energy cosmic ray electrons (LECRe) or protons (LECRp). In 2013, NuSTAR for
the first time resolved Sgr B2 hard X-ray emission on sub-arcminute scales. Two
prominent features are detected above 10 keV - a newly emerging cloud
G0.66-0.13 and the central 90" radius region containing two compact cores Sgr
B2(M) and Sgr B2(N) surrounded by diffuse emission. It is inconclusive whether
the remaining level of Sgr B2 emission is still decreasing or has reached a
constant background level. A decreasing Fe K emission can be best
explained by XRN while a constant background emission can be best explained by
LECRp. In the XRN scenario, the 3-79 keV Sgr B2 spectrum can well constrain the
past Sgr A* outburst, resulting in an outburst spectrum with a peak luminosity
of derived from the
maximum Compton-scattered continuum and the Fe K emission consistently.
The XRN scenario is preferred by the fast variability of G0.66-0.13, which
could be a molecular clump located in the Sgr B2 envelope reflecting the same
Sgr A* outburst. In the LECRp scenario, we derived the required CR ion power
and the CR ionization rate
. The Sgr B2 background level
X-ray emission will be a powerful tool to constrain GC CR population.Comment: 17 pages, 6 figures, submitted to Ap
A unified description for nuclear equation of state and fragmentation in heavy ion collisions
We propose a model that provides a unified description of nuclear equation of
state and fragmentations. The equation of state is evaluated in Bragg-Williams
as well as in Bethe-Peierls approximations and compared with that in the mean
field theory with Skyrme interactions. The model shows a liquid-gas type phase
transition. The nuclear fragment distributions are studied for different
densities at finite temperatures. Power law behavior for fragments is observed
at critical point. The study of fragment distribution and the second moment
shows that the thermal critical point coincides with the percolation
point at the critical density. High temperature behavior of the model shows
characteristics of chemical equilibrium.Comment: 20 pages in RevTex, 11 figures (uuencoded ps files), to appear in
Phys. Rev.
Properties of star-forming galaxies in a cluster and its surrounding structure at z=1.46
We conduct a narrow-band imaging survey of [OII] emitters over a 32'x23' area
in and around the XMMXCS J2215.9-1738 cluster at z=1.46 with
Subaru/Suprime-Cam, and select 380 [OII] emitting galaxies down to 1.4E-17
erg/s/cm2. Among them, 16 [OII] emitters in the cluster central region are
confirmed by NIR spectroscopy with Subaru/MOIRCS. We find that [OII] emitters
are distributed along filamentary large-scale structures around the cluster.
The z'-K vs K colour-magnitude diagram shows that a significantly higher
fraction of [OII] emitters is seen on the red sequence in the cluster core than
in other environments we define in this paper. It is likely that these red
galaxies are nearly passively evolving galaxies which host [OII] emitting AGNs,
rather than dust-reddened star-forming galaxies. We argue therefore that AGN
feedback may be one of the critical processes to quench star formation in
massive galaxies in high density regions. We also find that the cluster has
experienced high star formation activities at rates comparable to that in the
field at z=1.46. In addition, a mass-metallicity relation exists in the cluster
at z=1.46, which is similar to that of star-forming galaxies in the field at
z~2. These results all suggest that at z~1.5 star formation activity in the
cluster core becomes as high as those in low density environments and there is
apparently not yet a strong environmental dependence, except for the red
emitters.Comment: 19 pages, 17 figures, 4 tables, accepted for publication in MNRA
Nmnat1 protects neuronal function without altering phospho-tau pathology in a mouse model of tauopathy
OBJECTIVE: The nicotinamideânucleotide adenylyltransferase protein Nmnat1 is a potent inhibitor of axonal degeneration in models of acute axonal injury. Hyperphosphorylation and aggregation of the microtubuleâassociated protein Tau are associated with neurodegeneration in Alzheimer's Disease and other disorders. Previous studies have demonstrated that other Nmnat isoforms can act both as axonoprotective agents and have protein chaperone function, exerting protective effects in drosophila and mouse models of tauopathy. Nmnat1 targeted to the cytoplasm (cytNmnat1) is neuroprotective in a mouse model of neonatal hypoxiaâischemia, but the effect of cytNmnat1 on tauopathy remains unknown. METHODS: We examined the impact of overexpression of cytNmnat1 on tau pathology, neurodegeneration, and brain functional connectivity in the P301S mouse model of chronic tauopathy. RESULTS: Overexpression of cytNmnat1 preserved cortical neuron functional connectivity in P301S mice in vivo. However, whereas Nmnat1 overexpression decreased the accumulation of detergentâinsoluble tau aggregates in the cerebral cortex, it exerted no effect on immunohistochemical evidence of pathologic tau phosphorylation and misfolding, hippocampal atrophy, or inflammatory markers in P301S mice. INTERPRETATION: Our results demonstrate that cytNmnat1 partially preserves neuronal function and decreases biochemically insoluble tau in a mouse model of chronic tauopathy without preventing tau phosphorylation, formation of soluble aggregates, or tauâinduced inflammation and atrophy. Nmnat1 might thus represent a therapeutic target for tauopathies
G359.97-0.038: A Hard X-Ray Filament Associated with a Supernova Shell-Molecular Cloud Interaction
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