2,755 research outputs found
Alpha cluster condensation in 12C and 16O
A new -cluster wave function is proposed which is of the
-particle condensate type. Applications to C and O show
that states of low density close to the 3 resp. 4 -particle threshold
in both nuclei are possibly of this kind. It is conjectured that all
self-conjugate 4 nuclei may show similar features.Comment: 4 pages, 2 tables, 2 figure
Analysis of previous microscopic calculations for second state in C in terms of 3-alpha particle Bose-condensed state
The wave function of the second state of C which was obtained
long time ago by solving the microscopic 3 problem is shown to be
almost completely equivalent to the wave function of the 3 condensed
state which has been proposed recently by the present authors. This equivalence
of the wave functions is shown to hold in two cases where different effective
two-nucleon forces are adopted. This finding gives strong support for
interpreting the second state of C which is the key state for the
synthesis of C in stars ('Hoyle' state), and which is one of the typical
mysterious states in light nuclei, as a gas-like structure of three
particles, Bose-condensed into an identical s-wave function.Comment: revtex, 5 pages, 2 figures, submitted to Phys. Rev.
Trapping of Neutral Rubidium with a Macroscopic Three-Phase Electric Trap
We trap neutral ground-state rubidium atoms in a macroscopic trap based on
purely electric fields. For this, three electrostatic field configurations are
alternated in a periodic manner. The rubidium is precooled in a magneto-optical
trap, transferred into a magnetic trap and then translated into the electric
trap. The electric trap consists of six rod-shaped electrodes in cubic
arrangement, giving ample optical access. Up to 10^5 atoms have been trapped
with an initial temperature of around 20 microkelvin in the three-phase
electric trap. The observations are in good agreement with detailed numerical
simulations.Comment: 4 pages, 4 figure
Restoration of Isospin Symmetry in Highly Excited Nuclei
Explicit relations between the isospin mixing probability, the spreading
width of the Isobaric Analog State (IAS) and the
statistical decay width of the compound nucleus at finite excitation
energy, are derived by using the Feshbach projection formalism. The temperature
dependence of the isospin mixing probability is discussed quantitatively for
the first time by using the values of and of
calculated by means of microscopic models. It is shown that the
mixing probability remains essentially constant up to a temperature of the
order of 1 MeV and then decreases to about 1/4 of its zero temperature value,
at higher temperature than 3 MeV, due to the short decay time of the
compound system.Comment: 13 pages, 1 figure (PostScript file included). To appear in Phys.
Lett.
Studies on Rat Peritoneal Mast Cells 1. Purification of Mast Cells From Rat Peritoneal Cavity
To get a high recovery rate of mast cells from the rat peritoneal cavity, a new modified method was discussed using BSA density gradient. Three procedures, peritoneal lavage, washing of peritoneal cells and purification by BSA, were tested in this study, and the numbers of total cells and mast cells in each procedure were calculated. The recovery rate was the highest in BSA density gradient purification of the cells washed once with low speed centrifugation. The recovery rate was 73.7% and the number of mast cells taken from one rat was approximately 1.5×10(6). The purity of the cells with this procedure was 95.0% (range from 93.0 to 96.0%)
Small-scale convection signatures associated with strong plage solar magnetic field
In this work, we study and quantify properties of strong-field small-scale
convection and compare observed properties with those predicted by numerical
simulations. We analyze spectropolarimetric 630.25 nm data from a unipolar
ephemeral region near sun center. We use line-of-sight velocities and magnetic
field measurements obtained with Milne-Eddington inversion techniques along
with measured continuum intensities and Stokes V amplitude asymmetry at a
spatial resolution of 0.15 arcseconds to establish statistical relations
between the measured quantities. We also study these properties for different
types of distinct magnetic features, such as micropores, bright points,
ribbons, flowers and strings. We present the first direct observations of a
small-scale granular magneto-convection pattern within extended regions of
strong (more than 600 G average) magnetic field. Along the boundaries of the
flux concentrations we see mostly downflows and asymmetric Stokes V profiles,
consistent with synthetic line profiles calculated from MHD simulations. We
note the frequent occurrence of bright downflows along these boundaries. In the
interior of the flux concentrations, we observe an up/down flow pattern that we
identify as small-scale magnetoconvection, appearing similar to that of
field-free granulation but with scales 4 times smaller. Measured RMS velocities
are 70% of those of nearby field-free granulation, even though the average
radiative flux is not reduced. The interiors of these flux concentrations are
dominated by upflows.Comment: Accepted for publication in Astronomy and Astrophysic
Characterization of distinct subpopulations of hepatic macrophages in HFD/obese mice.
The current dogma is that obesity-associated hepatic inflammation is due to increased Kupffer cell (KC) activation. However, recruited hepatic macrophages (RHMs) were recently shown to represent a sizable liver macrophage population in the context of obesity. Therefore, we assessed whether KCs and RHMs, or both, represent the major liver inflammatory cell type in obesity. We used a combination of in vivo macrophage tracking methodologies and adoptive transfer techniques in which KCs and RHMs are differentially labeled with fluorescent markers. With these approaches, the inflammatory phenotype of these distinct macrophage populations was determined under lean and obese conditions. In vivo macrophage tracking revealed an approximately sixfold higher number of RHMs in obese mice than in lean mice, whereas the number of KCs was comparable. In addition, RHMs comprised smaller size and immature, monocyte-derived cells compared with KCs. Furthermore, RHMs from obese mice were more inflamed and expressed higher levels of tumor necrosis factor-α and interleukin-6 than RHMs from lean mice. A comparison of the MCP-1/C-C chemokine receptor type 2 (CCR2) chemokine system between the two cell types showed that the ligand (MCP-1) is more highly expressed in KCs than in RHMs, whereas CCR2 expression is approximately fivefold greater in RHMs. We conclude that KCs can participate in obesity-induced inflammation by causing the recruitment of RHMs, which are distinct from KCs and are not precursors to KCs. These RHMs then enhance the severity of obesity-induced inflammation and hepatic insulin resistance
Wave Packet Echoes in the Motion of Trapped Atoms
We experimentally demonstrate and systematically study the stimulated revival
(echo) of motional wave packet oscillations. For this purpose, we prepare wave
packets in an optical lattice by non-adiabatically shifting the potential and
stimulate their reoccurence by a second shift after a variable time delay. This
technique, analogous to spin echoes, enables one even in the presence of strong
dephasing to determine the coherence time of the wave packets. We find that for
strongly bound atoms it is comparable to the cooling time and much longer than
the inverse of the photon scattering rate
Cooling atomic motion with quantum interference
We theoretically investigate the quantum dynamics of the center of mass of
trapped atoms, whose internal degrees of freedom are driven in a
-shaped configuration with the lasers tuned at two-photon resonance.
In the Lamb-Dicke regime, when the motional wave packet is well localized over
the laser wavelenght, transient coherent population trapping occurs, cancelling
transitions at the laser frequency. In this limit the motion can be efficiently
cooled to the ground state of the trapping potential. We derive an equation for
the center-of-mass motion by adiabatically eliminating the internal degrees of
freedom. This treatment provides the theoretical background of the scheme
presented in [G. Morigi {\it et al}, Phys. Rev. Lett. {\bf 85}, 4458 (2000)]
and implemented in [C.F. Roos {\it et al}, Phys. Rev. Lett. {\bf 85}, 5547
(2000)]. We discuss the physical mechanisms determining the dynamics and
identify new parameters regimes, where cooling is efficient. We discuss
implementations of the scheme to cases where the trapping potential is not
harmonic.Comment: 11 pages, 3 figure
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