630 research outputs found
Sensing electric and magnetic fields with Bose-Einstein Condensates
We discuss the application of Bose-Einstein condensates (BECs) as sensors for
magnetic and electric fields. In an experimental demonstration we have brought
one-dimensional BECs close to micro-fabricated wires on an atom chip and
thereby reached a sensitivity to potential variations of ~10e-14eV at 3 micron
spatial resolution. We demonstrate the versatility of this sensor by measuring
a two-dimensional magnetic field map 10 micron above a 100-micron-wide wire. We
show how the transverse current-density component inside the wire can be
reconstructed from such maps. The field sensitivity in dependence on the
spatial resolution is discussed and further improvements utilizing Feshbach
resonances are outlined.Comment: 4 pages, 3 figure
Atom Chips: Fabrication and Thermal Properties
Neutral atoms can be trapped and manipulated with surface mounted microscopic
current carrying and charged structures. We present a lithographic fabrication
process for such atom chips based on evaporated metal films. The size limit of
this process is below 1m. At room temperature, thin wires can carry more
than 10A/cm current density and voltages of more than 500V. Extensive
test measurements for different substrates and metal thicknesses (up to 5
m) are compared to models for the heating characteristics of the
microscopic wires. Among the materials tested, we find that Si is the best
suited substrate for atom chips
Sigma_c Dbar and Lambda_c Dbar states in a chiral quark model
The S-wave Sigma_c Dbar and Lambda_c Dbar states with isospin I=1/2 and spin
S=1/2 are dynamically investigated within the framework of a chiral constituent
quark model by solving a resonating group method (RGM) equation. The results
show that the interaction between Sigma_c and Dbar is attractive, which
consequently results in a Sigma_c Dbar bound state with the binding energy of
about 5-42 MeV, unlike the case of Lambda_c Dbar state, which has a repulsive
interaction and thus is unbound. The channel coupling effect of Sigma_c Dbar
and Lambda_c Dbar is found to be negligible due to the fact that the gap
between the Sigma_c Dbar and Lambda_c Dbar thresholds is relatively large and
the Sigma_c Dbar and Lambda_c Dbar transition interaction is weak.Comment: 7 pages,2 figures. arXiv admin note: text overlap with
arXiv:nucl-th/0606056 by other author
Leveraging YouTube for Storage Management and Accessibility
In an effort to improve the users’ experience when accessing our institutional repository, we decided to add closed captioning to all videos. We investigated a number of options such as local streaming servers and vended products, but could not find one that could meet our needs in terms of accessibility, compatibility with our repository platform, and easy of storage and management of videos. We then decided to test YouTube as a possible solution. We were pleased to learn that YouTube had auto closed captioning/transcription, a method of merging previously transcribed text with videos posted in YouTube, and an easy method to correct closed captions on the fly. YouTube also allows users to search the transcript and moves them to that point in the video. Overall, YouTube has improved both the usability and accessibility of our institutional repository
Disorder Potentials near Lithographically Fabricated Atom Chips
We show that previously observed large disorder potentials in magnetic
microtraps for neutral atoms are reduced by about two orders of magnitude when
using atom chips with lithographically fabricated high quality gold layers.
Using one dimensional Bose-Einstein condensates, we probe the remaining
magnetic field variations at surface distances down to a few microns.
Measurements on a 100 um wide wire imply that residual variations of the
current flow result from local properties of the wire.Comment: submitted on September 24th, 200
An atom fiber for guiding cold neutral atoms
We present an omnidirectional matter wave guide on an atom chip. The
rotational symmetry of the guide is maintained by a combination of two current
carrying wires and a bias field pointing perpendicular to the chip surface. We
demonstrate guiding of thermal atoms around more than two complete turns along
a spiral shaped 25mm long curved path (curve radii down to 200m) at
various atom--surface distances (35-450m). An extension of the scheme for
the guiding of Bose-Einstein condensates is outlined
Matter-wave interferometry in a double well on an atom chip
Matter-wave interference experiments enable us to study matter at its most
basic, quantum level and form the basis of high-precision sensors for
applications such as inertial and gravitational field sensing. Success in both
of these pursuits requires the development of atom-optical elements that can
manipulate matter waves at the same time as preserving their coherence and
phase. Here, we present an integrated interferometer based on a simple,
coherent matter-wave beam splitter constructed on an atom chip. Through the use
of radio-frequency-induced adiabatic double-well potentials, we demonstrate the
splitting of Bose-Einstein condensates into two clouds separated by distances
ranging from 3 to 80 microns, enabling access to both tunnelling and isolated
regimes. Moreover, by analysing the interference patterns formed by combining
two clouds of ultracold atoms originating from a single condensate, we measure
the deterministic phase evolution throughout the splitting process. We show
that we can control the relative phase between the two fully separated samples
and that our beam splitter is phase-preserving
Thrombosis of a Superior Mesenteric Vein Aneurysm: Transarterial Thrombolysis and Transhepatic Aspiration Thrombectomy
We report the case of a 31-year-old woman presenting with abdominal pain due to acute thrombosis of a superior and inferior mesenteric vein aneurysm, which was treated by a combination of arterial thrombolysis and transhepatic thrombus aspiration. At the last follow-up CT, 21 months following this procedure, there was no evidence of rethrombosis, and the patient continues to do well under oral anticoagulation. The literature regarding these uncommon mesenteric vein aneurysms without portal vein involvement, as well as their treatment options, is reviewe
User-Focused Redesign: Using Survey and Usability Data to Redesign a Library Website
Are library websites meeting our users’ needs? Usability testing is one way to answer this question. Panelists will share the planning process and usability testing method employed for the redesign of an academic library website. Observations, video clips from the tests, and practical application of the findings will be shared
Long-Range Order in Electronic Transport through Disordered Metal Films
Ultracold atom magnetic field microscopy enables the probing of current flow
patterns in planar structures with unprecedented sensitivity. In
polycrystalline metal (gold) films we observe long-range correlations forming
organized patterns oriented at +/- 45 deg relative to the mean current flow,
even at room temperature and at length scales orders of magnitude larger than
the diffusion length or the grain size. The preference to form patterns at
these angles is a direct consequence of universal scattering properties at
defects. The observed amplitude of the current direction fluctuations scales
inversely to that expected from the relative thickness variations, the grain
size and the defect concentration, all determined independently by standard
methods. This indicates that ultracold atom magnetometry enables new insight
into the interplay between disorder and transport
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