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

Antiresonance phase shift in strongly coupled cavity QED

We investigate phase shifts in the strong coupling regime of single-atom cavity quantum electrodynamics (QED). On the light transmitted through the system, we observe a phase shift associated with an antiresonance and show that both its frequency and width depend solely on the atom, despite the strong coupling to the cavity. This shift is optically controllable and reaches 140 degrees - the largest ever reported for a single emitter. Our result offers a new technique for the characterization of complex integrated quantum circuits.Comment: 5 pages, 5 figure

The Robust Network Loading Problem under Hose Demand Uncertainty: Formulation, Polyhedral Analysis, and Computations

Cataloged from PDF version of article.We consider the network loading problem (NLP) under a polyhedral uncertainty description of traffic demands. After giving a compact multicommodity flow formulation of the problem, we state a decomposition property obtained from projecting out the flow variables. This property considerably simplifies the resulting polyhedral analysis and computations by doing away with metric inequalities. Then we focus on a specific choice of the uncertainty description, called the “hose model,” which specifies aggregate traffic upper bounds for selected endpoints of the network. We study the polyhedral aspects of the NLP under hose demand uncertainty and use the results as the basis of an efficient branch-and-cut algorithm. The results of extensive computational experiments on well-known network design instances are reported

Quantum projection noise limited interferometry with coherent atoms in a Ramsey type setup

Every measurement of the population in an uncorrelated ensemble of two-level systems is limited by what is known as the quantum projection noise limit. Here, we present quantum projection noise limited performance of a Ramsey type interferometer using freely propagating coherent atoms. The experimental setup is based on an electro-optic modulator in an inherently stable Sagnac interferometer, optically coupling the two interfering atomic states via a two-photon Raman transition. Going beyond the quantum projection noise limit requires the use of reduced quantum uncertainty (squeezed) states. The experiment described demonstrates atom interferometry at the fundamental noise level and allows the observation of possible squeezing effects in an atom laser, potentially leading to improved sensitivity in atom interferometers.Comment: 8 pages, 8 figures, published in Phys. Rev.

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

On Fatou type convergence of higher derivatives of certain nonlinear singular integral operators

The present paper concerns with the Fatou type convergence properties of the $r-th$ and $(r+1)-th$ derivatives of the nonlinear singular integral operators defined as $$\left( I_{\lambda}f\right) (x)=\int\limits_{a}^{b}K_{\lambda}(t-x,f(t))\,{\rm d}t,\,\,\,\,\,\,\,x\in\left( a,b\right) ,$$ acting on functions defined on an arbitrary interval $\left( a,b\right) ,$ where the kernel $K_{\lambda}$ satisfies some suitable assumptions. The present study is a continuation and extension of the results established in the paper [7]

Continuous parametric feedback cooling of a single atom in an optical cavity

We demonstrate a new feedback algorithm to cool a single neutral atom trapped inside a standing-wave optical cavity. The algorithm is based on parametric modulation of the confining potential at twice the natural oscillation frequency of the atom, in combination with fast and repetitive atomic position measurements. The latter serve to continuously adjust the modulation phase to a value for which parametric excitation of the atomic motion is avoided. Cooling is limited by the measurement back action which decoheres the atomic motion after only a few oscillations. Nonetheless, applying this feedback scheme to a ~ 5 kHz oscillation mode increases the average storage time of a single atom in the cavity by a factor of 60 to more than 2 seconds. In contrast to previous feedback schemes, our algorithm is also capable of cooling a much faster ~ 500 kHz oscillation mode within just microseconds. This demonstrates that parametric cooling is a powerful technique that can be applied in all experiments where optical access is limited.Comment: 7 pages, 5 figure

Optically guided linear Mach Zehnder atom interferometer

We demonstrate a horizontal, linearly guided Mach Zehnder atom interferometer in an optical waveguide. Intended as a proof-of-principle experiment, the interferometer utilises a Bose-Einstein condensate in the magnetically insensitive |F=1,mF=0> state of Rubidium-87 as an acceleration sensitive test mass. We achieve a modest sensitivity to acceleration of da = 7x10^-4 m/s^2. Our fringe visibility is as high as 38% in this optically guided atom interferometer. We observe a time-of-flight in the waveguide of over half a second, demonstrating the utility of our optical guide for future sensors.Comment: 6 pages, 3 figures. Submitted to Phys. Rev.