1,289 research outputs found
Crystal structures of the human Dysferlin inner DysF domain
Background: Mutations in dysferlin, the first protein linked with the cell membrane repair mechanism, causes a group of muscular dystrophies called dysferlinopathies. Dysferlin is a type two-anchored membrane protein, with a single C terminal trans-membrane helix, and most of the protein lying in cytoplasm. Dysferlin contains several C2 domains and two DysF domains which are nested one inside the other. Many pathogenic point mutations fall in the DysF domain region.
Results: We describe the crystal structure of the human dysferlin inner DysF domain with a resolution of 1.9 Angstroms. Most of the pathogenic mutations are part of aromatic/arginine stacks that hold the domain in a folded conformation. The high resolution of the structure show that these interactions are a mixture of parallel ring/guanadinium stacking, perpendicular H bond stacking and aliphatic chain packing.
Conclusions: The high resolution structure of the Dysferlin DysF domain gives a template on which to interpret in detail the pathogenic mutations that lead to disease
Rb-85 tunable-interaction Bose-Einstein condensate machine
We describe our experimental setup for creating stable Bose-Einstein
condensates of Rb-85 with tunable interparticle interactions. We use
sympathetic cooling with Rb-87 in two stages, initially in a tight
Ioffe-Pritchard magnetic trap and subsequently in a weak, large-volume crossed
optical dipole trap, using the 155 G Feshbach resonance to manipulate the
elastic and inelastic scattering properties of the Rb-85 atoms. Typical Rb-85
condensates contain 4 x 10^4 atoms with a scattering length of a=+200a_0. Our
minimalist apparatus is well-suited to experiments on dual-species and spinor
Rb condensates, and has several simplifications over the Rb-85 BEC machine at
JILA (Papp, 2007; Papp and Wieman, 2006), which we discuss at the end of this
article.Comment: 10 pages, 8 figure
Cold atom gravimetry with a Bose-Einstein Condensate
We present a cold atom gravimeter operating with a sample of Bose-condensed
Rubidium-87 atoms. Using a Mach-Zehnder configuration with the two arms
separated by a two-photon Bragg transition, we observe interference fringes
with a visibility of 83% at T=3 ms. We exploit large momentum transfer (LMT)
beam splitting to increase the enclosed space-time area of the interferometer
using higher-order Bragg transitions and Bloch oscillations. We also compare
fringes from condensed and thermal sources, and observe a reduced visibility of
58% for the thermal source. We suspect the loss in visibility is caused partly
by wavefront aberrations, to which the thermal source is more susceptible due
to its larger transverse momentum spread. Finally, we discuss briefly the
potential advantages of using a coherent atomic source for LMT, and present a
simple mean-field model to demonstrate that with currently available
experimental parameters, interaction-induced dephasing will not limit the
sensitivity of inertial measurements using freely-falling, coherent atomic
sources.Comment: 6 pages, 4 figures. Final version, published PR
Bosenova and three-body loss in a Rb-85 Bose-Einstein condensate
Collapsing Bose-Einstein condensates are rich and complex quantum systems for
which quantitative explanation by simple models has proved elusive. We present
new experimental data on the collapse of high density Rb-85 condensates with
attractive interactions and find quantitative agreement with the predictions of
the Gross-Pitaevskii equation. The collapse data and measurements of the decay
of atoms from our condensates allow us to put new limits on the value of the
Rb-85 three-body loss coefficient K_3 at small positive and negative scattering
lengths.Comment: 6 pages, 5 figure
Optically trapped atom interferometry using the clock transition of large Rb-87 Bose-Einstein condensates
We present a Ramsey-type atom interferometer operating with an optically
trapped sample of 10^6 Bose-condensed Rb-87 atoms. The optical trap allows us
to couple the |F =1, mF =0>\rightarrow |F =2, mF =0> clock states using a
single photon 6.8GHz microwave transition, while state selective readout is
achieved with absorption imaging. Interference fringes with contrast
approaching 100% are observed for short evolution times. We analyse the process
of absorption imaging and show that it is possible to observe atom number
variance directly, with a signal-to-noise ratio ten times better than the
atomic projection noise limit on 10^6 condensate atoms. We discuss the
technical and fundamental noise sources that limit our current system, and
outline the improvements that can be made. Our results indicate that, with
further experimental refinements, it will be possible to produce and measure
the output of a sub-shot-noise limited, large atom number BEC-based
interferometer.
In an addendum to the original paper, we attribute our inability to observe
quantum projection noise to the stability of our microwave oscillator and
background magnetic field. Numerical simulations of the Gross-Pitaevskii
equations for our system show that dephasing due to spatial dynamics driven by
interparticle interactions account for much of the observed decay in fringe
visibility at long interrogation times. The simulations show good agreement
with the experimental data when additional technical decoherence is accounted
for, and suggest that the clock states are indeed immiscible. With smaller
samples of 5 \times 10^4 atoms, we observe a coherence time of {\tau} =
(1.0+0.5-0.3) s.Comment: 22 pages, 6 figures Addendum: 11 pages, 6 figure
Estimating the Economic Impact of Vacation Home Rentals in Florida
This report takes an in-depth look at the economic impact of the Florida vacation rental home industry and its ripple effects across the state. It includes an estimate of the magnitude of the industry\u27s impact on Florida\u27s economy as well as profiles of the main stakeholders who generate this impact.
The report focuses on the economic impact of the vacation rental home industry in 25 Florida counties selected by the client, Florida Realtors® (Escambia, Santa Rosa, Okaloosa, Walton, Bay, Gulf, Franklin, Nassau, Duval, Pinellas, Hillsborough, Manatee, Sarasota, Charlotte, Lee, Collier, Monroe, Miami-Dade, Broward, Palm Beach, Orange, Osceola, Brevard, Volusia, and Flagler). When combined, these 25 counties include 89.3% of the total amount of registered vacation rental homes in the state of Florida
Measurement of inelastic losses in a sample of ultracold Rb-85
We report on the observation and characterisation of an inelastic loss
feature in collisions between ultracold Rb-85 |F=2, m_F=-2> atoms at a magnetic
field of 220 G. Our apparatus creates ultracold Rb-85 clouds by sympathetic
cooling with a Rb-87 reservoir, and can produce pure Rb-87 condensates of 10^6
atoms by a combination of evaporative cooling in a quadrupole-Ioffe magnetic
trap and further evaporation in a weak, large-volume optical dipole trap. By
combining Rb-85 and Rb-87 atoms collected in a dual-species magneto-optical
trap and selectively evaporating the heavier isotope, we demonstrate strong
sympathetic cooling of the Rb-85 cloud, increasing its phase space density by
three orders of magnitude with no detectable loss in number. We have used
ultracold samples created in this way to observe the variation of inelastic
loss in ultracold Rb-85 as a function of magnetic field near the 155 G Feshbach
resonance. We have also measured a previously unobserved loss feature at
219.9(1) G with a width of 0.28(6) G, which we associate with a narrow Feshbach
resonance predicted by theory.Comment: 4 pages, 3 figures, content change
Precision atomic gravimeter based on Bragg diffraction
We present a precision gravimeter based on coherent Bragg diffraction of
freely falling cold atoms. Traditionally, atomic gravimeters have used
stimulated Raman transitions to separate clouds in momentum space by driving
transitions between two internal atomic states. Bragg interferometers utilize
only a single internal state, and can therefore be less susceptible to
environmental perturbations. Here we show that atoms extracted from a
magneto-optical trap using an accelerating optical lattice are a suitable
source for a Bragg atom interferometer, allowing efficient beamsplitting and
subsequent separation of momentum states for detection. Despite the inherently
multi-state nature of atom diffraction, we are able to build a Mach-Zehnder
interferometer using Bragg scattering which achieves a sensitivity to the
gravitational acceleration of with an
integration time of 1000s. The device can also be converted to a gravity
gradiometer by a simple modification of the light pulse sequence.Comment: 13 pages, 11 figure
High expression of nicotinamide N-methyltransferase in patients with sporadic Alzheimer’s disease
We have previously shown that the expression of nicotinamide N-methyltransferase (NNMT) is significantly increased in the brains of patients who have died of Parkinson’s disease (PD). In this study, we have compared the expression of NNMT in post-mortem medial temporal lobe, hippocampus and cerebellum of 10 Alzheimer’s disease (AD) and 9 non-disease control subjects using a combination of quantitative Western blotting, immunohistochemistry and dual-label confocal microscopy coupled with quantitative analysis of colocalisation. NNMT was detected as a single protein of 29 kDa in both AD and non-disease control brains, which was significantly increased in AD medial temporal lobe compared to non-disease controls (7.5-fold, P < 0.026). There was no significant difference in expression in the cerebellum (P = 0.91). NNMT expression in AD medial temporal lobe and hippocampus was present in cholinergic neurones with no glial localisation. Cell-type expression was identical in both non-disease control and AD tissues. These results are the first to show, in a proof-of-concept study using a small patient cohort, that NNMT protein expression is increased in the AD brain and is present in neurones which degenerate in AD. These results suggest that the elevation of NNMT may be a common feature of many neurodegenerative diseases. Confirmation of this overexpression using a larger AD patient cohort will drive the future development of NNMT-targetting therapeutics which may slow or stop the disease pathogenesis, in contrast to current therapies which solely address AD symptoms
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