1,032 research outputs found
Vacuum-stimulated cooling of single atoms in three dimensions
Taming quantum dynamical processes is the key to novel applications of
quantum physics, e.g. in quantum information science. The control of
light-matter interactions at the single-atom and single-photon level can be
achieved in cavity quantum electrodynamics, in particular in the regime of
strong coupling where atom and cavity form a single entity. In the optical
domain, this requires permanent trapping and cooling of an atom in a
micro-cavity. We have now realized three-dimensional cavity cooling and
trapping for an orthogonal arrangement of cooling laser, trap laser and cavity
vacuum. This leads to average single-atom trapping times exceeding 15 seconds,
unprecedented for a strongly coupled atom under permanent observation.Comment: 4 pages, 4 figure
Recommended from our members
A high resolution extreme ultraviolet spectrometer system optimized for harmonic spectroscopy and XUV beam analysis
We present a modular extreme ultraviolet (XUV) spectrometer system optimized for a broad spectral range of 12-41 nm (30-99 eV) with a high spectral resolution of λ/Δλ 784 ± 89. The spectrometer system has several operation modes for (1) XUV beam inspection, (2) angular spectral analysis, and (3) imaging spectroscopy. These options allow for a versatile use in high harmonic spectroscopy and XUV beam analysis. The high performance of the spectrometer is demonstrated using a novel cross-sectional imaging method called XUV coherence tomography. © 2019 Author(s)
Outlying HII Regions in HI-Selected Galaxies
We present results from the first systematic search for outlying HII regions,
as part of a sample of 96 emission-line point sources (referred to as ELdots -
emission-line dots) derived from the NOAO Survey for Ionization in Neutral Gas
Galaxies (SINGG). Our automated ELdot-finder searches SINGG narrow-band and
continuum images for high equivalent width point sources outside the optical
radius of the target galaxy (> 2 X r25 in the R-band). Follow-up longslit
spectroscopy and deep GALEX images (exposure time > 1000 s) distinguish
outlying HII regions from background galaxies whose strong emission lines
([OIII], Hbeta or [OII]) have been redshifted into the SINGG bandpass. We find
that these deep GALEX images can serve as a substitute for spectroscopic
follow-up because outlying HII regions separate cleanly from background
galaxies in color-color space. We identify seven SINGG systems with outlying
massive star formation that span a large range in Halpha luminosities
corresponding to a few O stars in the most nearby cases, and unresolved dwarf
satellite companion galaxies in the most distant cases. Six of these seven
systems feature galaxies with nearby companions or interacting galaxies.
Furthermore, our results indicate that some outlying HII regions are linked to
the extended-UV disks discovered by GALEX, representing emission from the most
massive O stars among a more abundant population of lower mass (or older) star
clusters. The overall frequency of outlying HII regions in this sample of
gas-rich galaxies is 8 - 11% when we correct for background emission-line
galaxy contamination (~75% of ELdots).Comment: 20 pages, 14 Figures, Accepted by A
Characterization of elastic scattering near a Feshbach resonance in rubidium 87
The s-wave scattering length for elastic collisions between 87Rb atoms in the
state |f,m_f>=|1,1> is measured in the vicinity of a Feshbach resonance near
1007 G. Experimentally, the scattering length is determined from the mean-field
driven expansion of a Bose-Einstein condensate in a homogeneous magnetic field.
The scattering length is measured as a function of the magnetic field and
agrees with the theoretical expectation. The position and the width of the
resonance are determined to be 1007.40 G and 0.20 G, respectively.Comment: 4 pages, 2 figures minor revisions: added Ref.6, included error bar
Topology effects in molecular organic electronic materials : pyrene and azupyrene
Abstract: Pyrene derivatives play a prominent role in organic electronic devices, including field effect transistors, light emitting diodes, and solar cells. The flexibility in the desired properties has previously been achieved by variation of substituents at the periphery of the pyrene backbone. In contrast, the influence of the topology of the central π‐electron system on the relevant properties such as the band gap or the fluorescence behavior has not yet been addressed. In this work, pyrene is compared with its structural isomer azupyrene, which has a π‐electron system with non‐alternant topology. Using photoelectron spectroscopy, near edge X‐ray absorption fine structure spectroscopy, and other methods, it is shown that the electronic band gap of azupyrene is by 0.72 eV smaller than that of pyrene. The difference of the optical band gaps is even larger with 1.09 eV, as determined by ultraviolet–visible absorption spectroscopy. The non‐alternant nature of azupyrene is also associated with a more localized charge distribution. Further insight is provided by density functional theory (DFT) calculations of the molecular properties and ab initio coupled cluster calculations of the optical transitions. The concept of aromaticity is used to interpret the major topology‐related differences
Gene Expression Analysis of Zebrafish Heart Regeneration
Mammalian hearts cannot regenerate. In contrast, zebrafish hearts regenerate even when up to 20% of the ventricle is amputated. The mechanism of zebrafish heart regeneration is not understood. To systematically characterize this process at the molecular level, we generated transcriptional profiles of zebrafish cardiac regeneration by microarray analyses. Distinct gene clusters were identified based on temporal expression patterns. Genes coding for wound response/inflammatory factors, secreted molecules, and matrix metalloproteinases are expressed in regenerating heart in sequential patterns. Comparisons of gene expression profiles between heart and fin regeneration revealed a set of regeneration core molecules as well as tissue-specific factors. The expression patterns of several secreted molecules around the wound suggest that they play important roles in heart regeneration. We found that both platelet-derived growth factor-a and -b (pdgf-a and pdgf-b) are upregulated in regenerating zebrafish hearts. PDGF-B homodimers induce DNA synthesis in adult zebrafish cardiomyocytes. In addition, we demonstrate that a chemical inhibitor of PDGF receptor decreases DNA synthesis of cardiomyocytes both in vitro and in vivo during regeneration. Our data indicate that zebrafish heart regeneration is associated with sequentially upregulated wound healing genes and growth factors and suggest that PDGF signaling is required
Metal enrichment processes
There are many processes that can transport gas from the galaxies to their
environment and enrich the environment in this way with metals. These metal
enrichment processes have a large influence on the evolution of both the
galaxies and their environment. Various processes can contribute to the gas
transfer: ram-pressure stripping, galactic winds, AGN outflows, galaxy-galaxy
interactions and others. We review their observational evidence, corresponding
simulations, their efficiencies, and their time scales as far as they are known
to date. It seems that all processes can contribute to the enrichment. There is
not a single process that always dominates the enrichment, because the
efficiencies of the processes vary strongly with galaxy and environmental
properties.Comment: 18 pages, 8 figures, accepted for publication in Space Science
Reviews, special issue "Clusters of galaxies: beyond the thermal view",
Editor J.S. Kaastra, Chapter 17; work done by an international team at the
International Space Science Institute (ISSI), Bern, organised by J.S.
Kaastra, A.M. Bykov, S. Schindler & J.A.M. Bleeke
Multiplicity dependence of jet-like two-particle correlations in p-Pb collisions at = 5.02 TeV
Two-particle angular correlations between unidentified charged trigger and
associated particles are measured by the ALICE detector in p-Pb collisions at a
nucleon-nucleon centre-of-mass energy of 5.02 TeV. The transverse-momentum
range 0.7 5.0 GeV/ is examined,
to include correlations induced by jets originating from low
momen\-tum-transfer scatterings (minijets). The correlations expressed as
associated yield per trigger particle are obtained in the pseudorapidity range
. The near-side long-range pseudorapidity correlations observed in
high-multiplicity p-Pb collisions are subtracted from both near-side
short-range and away-side correlations in order to remove the non-jet-like
components. The yields in the jet-like peaks are found to be invariant with
event multiplicity with the exception of events with low multiplicity. This
invariance is consistent with the particles being produced via the incoherent
fragmentation of multiple parton--parton scatterings, while the yield related
to the previously observed ridge structures is not jet-related. The number of
uncorrelated sources of particle production is found to increase linearly with
multiplicity, suggesting no saturation of the number of multi-parton
interactions even in the highest multiplicity p-Pb collisions. Further, the
number scales in the intermediate multiplicity region with the number of binary
nucleon-nucleon collisions estimated with a Glauber Monte-Carlo simulation.Comment: 23 pages, 6 captioned figures, 1 table, authors from page 17,
published version, figures at
http://aliceinfo.cern.ch/ArtSubmission/node/161
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