1,868 research outputs found
Efficient Two-dimensional Subrecoil Raman Cooling of Atoms in a Tripod Configuration
We present an efficient method for subrecoil cooling of neutral atoms by
applying Raman cooling in 2D to a four-level tripod-system. The atoms can be
cooled simultaneously in two directions using only three laser beams. We
describe the cooling process with a simple model showing that the momentum
distribution can be rapidly narrowed to velocity spread down to
, corresponding to effective temperature equal to
. This method opens new possibilities for cooling of neutral
atoms.Comment: 6 pages, 3 figure
Three-dimensional atom localization by laser fields in a four-level tripod system
We present a scheme for high-precision three-dimensional (3D) localization by the measurement of the atomic-level population. The scheme is applied to a four-level tripod-type atom coupled by three strong standing waves and a probe running wave. As a result, the atom can be localized in volumes that are substantially smaller than a cubic optical wavelength, which is achieved by the increase of standing-wave intensities. The upper-level distribution depends crucially on the atom-field coupling and it forms 3D periodic structures composed of spheres, hourglasses, bowls, donuts, or deformed barrels.</p
Riemann-Hilbert problem, integrability and reductions
The present paper is dedicated to integrable models with Mikhailov reduction
groups Their Lax representation allows us to prove,
that their solution is equivalent to solving Riemann-Hilbert problems, whose
contours depend on the realization of the -action on the spectral
parameter. Two new examples of Nonlinear Evolution Equations (NLEE) with
symmetries are presented.Comment: 19 pages, 3 figures, Dedicated to Darryl Holm's 70th birthda
Robust two-dimensional subrecoil Raman cooling by adiabatic transfer in a tripod atomic system
We demonstrate two-dimensional robust Raman cooling in a four-level tripod
system, in which velocity-selective population transfer is achieved by a STIRAP
pulse. In contrast to basic 2D Raman cooling with square envelope pulses [Phys.
Rev. A 83, 023407 (2011)], the technique presented here allows for a wide
variation in the pulse duration and amplitude once the adiabaticity criterion
is satisfied. An efficient population transfer together with attaining of a
narrow spread of the resonant-velocity group leads to the narrowing of the
velocity-distribution spread down to , corresponding to an
effective temperature equal to . This robust method opens
new possibilities for cooling of neutral atoms.Comment: 8 pages, 3 figure
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STRA13 Interacts with STAT3 and Modulates Transcription of STAT3-dependent Targets
STRA13 is a pVHL-dependent bHLH transcription factor up-regulated on the mRNA level in multiple cancer cell lines and implicated recently in the regulation of immune cell homeostasis and autoimmunity. In searching for STRA13-interacting proteins with oncogenic potential by the yeast two-hybrid screening, we identified STAT3β as a STRA13-binding partner. We showed that STRA13 binds predominantly to phosphorylated (active) STAT3 α and β isoforms via its HLH and C-terminal regions. We also found that STRA13 was able to activate transcription from STAT-dependent cis-elements. Expression of endogenous STRA13 was shown to be cytokine-inducible, consistent with STRA13 involvement in STAT-dependent transcription regulation. We demonstrated that the STAT3-regulated promoter of the pro-apoptotic Fas gene was activated upon STRA13 over-expression and that co-expression of STRA13 with STAT3β or STAT3α modulated the transcriptional outcome. Forced expression of STRA13 induced apoptosis, in agreement with the STRA13 activation effect on the Fas promoter. Simultaneous expression of STRA13 and STAT3β resulted in alleviation of the STRA13 pro-apoptotic effect. Thus, for the first time, we identify STRA13 as a STAT3 partner and provide a consistent line of evidence for STRA13 involvement into regulation of apoptosis via the STAT pathways
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