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Campus & alumni news
Boston University Medicine was published by the Boston University Medical Campus, and presented stories on events and topics of interest to members of the BU Medical Campus community. It followed the discontinued publication Centerscope as Boston University Medicine from 1991-2005, and was continued as Campus & Alumni News from 2006-2013 before returning to the title Boston University Medicine from 2014-present
Nonlinear Dynamics of a Bose-Einstein Condensate in a Magnetic Waveguide
We have studied the internal and external dynamics of a Bose-Einstein
condensate in an anharmonic magnetic waveguide. An oscillating condensate
experiences a strong coupling between the center of mass motion and the
internal collective modes. Due to the anharmonicity of the magnetic potential,
not only the center of mass motion shows harmonic frequency generation, but
also the internal dynamics exhibit nonlinear frequency mixing. We describe the
data with a theoretical model to high accuracy. For strong excitations we test
the experimental data for indications of a chaotic behavior.Comment: 4 pages, 4 figure
Investigation of peak shapes in the MIBETA experiment calibrations
In calorimetric neutrino mass experiments, where the shape of a beta decay
spectrum has to be precisely measured, the understanding of the detector
response function is a fundamental issue. In the MIBETA neutrino mass
experiment, the X-ray lines measured with external sources did not have
Gaussian shapes, but exhibited a pronounced shoulder towards lower energies. If
this shoulder were a general feature of the detector response function, it
would distort the beta decay spectrum and thus mimic a non-zero neutrino mass.
An investigation was performed to understand the origin of the shoulder and its
potential influence on the beta spectrum. First, the peaks were fitted with an
analytic function in order to determine quantitatively the amount of events
contributing to the shoulder, also depending on the energy of the calibration
X-rays. In a second step, Montecarlo simulations were performed to reproduce
the experimental spectrum and to understand the origin of its shape. We
conclude that at least part of the observed shoulder can be attributed to a
surface effect
Investigation of planetary ionospheres
Feasibility of using radio sounding techniques to investigate ionospheric properties of planet
Diffraction of a Bose-Einstein condensate from a Magnetic Lattice on a Micro Chip
We experimentally study the diffraction of a Bose-Einstein condensate from a
magnetic lattice, realized by a set of 372 parallel gold conductors which are
micro fabricated on a silicon substrate. The conductors generate a periodic
potential for the atoms with a lattice constant of 4 microns. After exposing
the condensate to the lattice for several milliseconds we observe diffraction
up to 5th order by standard time of flight imaging techniques. The experimental
data can be quantitatively interpreted with a simple phase imprinting model.
The demonstrated diffraction grating offers promising perspectives for the
construction of an integrated atom interferometer.Comment: 4 pages, 4 figure
The Hard X-Ray View of Reflection, Absorption, and the Disk-Jet Connection in the Radio-Loud AGN 3C 33
We present results from Suzaku and Swift observations of the nearby radio
galaxy 3C 33, and investigate the nature of absorption, reflection, and jet
production in this source. We model the 0.5-100 keV nuclear continuum with a
power law that is transmitted either through one or more layers of pc-scale
neutral material, or through a modestly ionized pc-scale obscurer. The standard
signatures of reflection from a neutral accretion disk are absent in 3C 33:
there is no evidence of a relativistically blurred Fe K emission line,
and no Compton reflection hump above 10 keV. We find the upper limit to the
neutral reflection fraction is R<0.41 for an e-folding energy of 1 GeV. We
observe a narrow, neutral Fe K line, which is likely to originate at
least 2,000 R_s from the black hole. We show that the weakness of reflection
features in 3C 33 is consistent with two interpretations: either the inner
accretion flow is highly ionized, or the black-hole spin configuration is
retrograde with respect to the accreting material.Comment: 12 pages, 11 figures, 4 tables. Accepted for publication in Ap
Formation of ultracold LiCs molecules
We present the first observation of ultracold LiCs molecules. The molecules
are formed in a two-species magneto-optical trap and detected by two-photon
ionization and time-of-flight mass spectrometry. The production rate
coefficient is found to be in the range 10^{-18}\unit{cm^3s^{-1}} to
10^{-16}\unit{cm^3s^{-1}}, at least an order of magnitude smaller than for
other heteronuclear diatomic molecules directly formed in a magneto-optical
trap.Comment: 8 pages, 2 figure
Review of the Refeeding Syndrome
Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/142310/1/ncp0625.pd
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