A Waveguide for Bose-Einstein Condensates

We report on the creation of Bose-Einstein condensates of $^{87}$Rb in a specially designed hybrid, dipole and magnetic trap. This trap naturally allows the coherent transfer of matter waves into a pure dipole potential waveguide based on a doughnut beam. Specifically, we present studies of the coherence of the ensemble in the hybrid trap and during the evolution in the waveguide by means of an autocorrelation interferometer scheme. By monitoring the expansion of the ensemble in the waveguide we observe a mean field dominated acceleration on a much longer time scale than in the free 3D expansion. Both the autocorrelation interference and the pure expansion measurements are in excellent agreement with theoretical predictions of the ensemble dynamics

Local characterization of hindered Brownian motion by using digital video microscopy and 3D particle tracking

This is the author accepted manuscript. The final version is available from the publisher via the DOI in this record.In this article we present methods for measuring hindered Brownian motion in the confinement of complex 3D geometries using digital video microscopy. Here we discuss essential features of automated 3D particle tracking as well as diffusion data analysis. By introducing local mean squared displacement-vs-time curves, we are able to simultaneously measure the spatial dependence of diffusion coefficients, tracking accuracies and drift velocities. Such local measurements allow a more detailed and appropriate description of strongly heterogeneous systems as opposed to global measurements. Finite size effects of the tracking region on measuring mean squared displacements are also discussed. The use of these methods was crucial for the measurement of the diffusive behavior of spherical polystyrene particles (505 nm diameter) in a microfluidic chip. The particles explored an array of parallel channels with different cross sections as well as the bulk reservoirs. For this experiment we present the measurement of local tracking accuracies in all three axial directions as well as the diffusivity parallel to the channel axis while we observed no significant flow but purely Brownian motion. Finally, the presented algorithm is suitable also for tracking of fluorescently labeled particles and particles driven by an external force, e.g., electrokinetic or dielectrophoretic forces.S.L.D. acknowledges funding from the German Academic Exchange Service (DAAD) and the German National Academic Foundation. S.P. and U.F.K. were supported by an ERC starting grant. S.P. also acknowledges the support from the Leverhulme Trust and the Newton Trust through an Early Career Fellowship

Bayesian inference for ultralow velocity zones in the Earth's lowermost mantle: complex ULVZ beneath the east of the Philippines

Ultralow velocity zones (ULVZs) are small-scale structures with a sharp decrease in S and P wave velocity, and an increase in the density on the top of the Earth's core-mantle boundary. The ratio of S and P wave velocity reduction and density anomaly are important to understanding whether ULVZs consist of partial melt or chemically distinct material. However, existing methods such as forward waveform modeling that utilize 1-D and 2-D Earth-structure models face challenges when trying to uniquely quantify ULVZ properties because of inherent nonuniqueness and nonlinearity. This paper develops a Bayesian inversion for ULVZ parameters and uncertainties with rigorous noise treatment to address these challenges. The posterior probability density of the ULVZ parameters (the solution to the inverse problem) is sampled by the Metropolis-Hastings algorithm. To improve sampling efficiency, parallel tempering is applied by simulating a sequence of tempered Markov chains in parallel and allowing information exchange between chains. First, the Bayesian inversion is applied to simulated noisy data for a realistic ULVZ model. Then, measured data sampling the lowermost mantle under the Philippine Sea are considered. Cluster analysis and visual waveform inspection suggest that two distinct classes of ScP (S waves converted to, and reflected as, P waves) waves exist in this region. The distinct waves likely correspond to lateral variability in the lowermost mantle properties in a NE-SW direction. For the NE area, Bayesian model selection identifies a two-layer model with a gradual density increase as a function of depth as optimal. This complex ULVZ structure can be due to the percolation of iron-enriched, molten material in the lowermost mantle. The results for the SW area are more difficult to interpret, which may be due to the limited number of data available (too few waveforms to appropriately reduce noise) and/or complex 2-D and 3-D structures that cannot be explained properly by the 1-D models required by our inversion approach. In particular, the complex waveforms require highly layered 1-D models to fit the data. These models appear physically unreasonable and suggest that the SW region cannot be explained by 1-D structure.National Collaborative Research Infrastructure Strategy (NCRIS) and the Education Investment Fund (EIF3)

Channel-facilitated diffusion boosted by particle binding at the channel entrance

This is the final version of the article. Available from the publisher via the DOI in this record.We investigate single-file diffusion of Brownian particles in arrays of closely confining microchannels permeated by a variety of attractive optical potentials and connecting two baths with equal particle concentration. We simultaneously test free diffusion in the channel, diffusion in optical traps coupled in the center of the channel, and diffusion in traps extending into the baths. We found that both classes of attractive optical potentials enhance the translocation rate through the channel with respect to free diffusion. Surprisingly, for the latter class of potentials we measure a 40-fold enhancement in the translocation rate with respect to free diffusion and find a sublinear power law dependence of the translocation rate on the average number of particles in the channel. Our results reveal the function of particle binding at the channel entrances for diffusive transport and open the way to a better understanding of membrane transport and design of synthetic membranes with enhanced diffusion rate.S. P. acknowledges support from the Leverhulme and Newton Trust through an Early Career Fellowship. S. L. D. acknowledges funding from the German Academic Exchange Service (DAAD) and the German National Academic Foundation. U. F. K. was supported by an ERC starting grant

Anisotropic diffusion of spherical particles in closely confining microchannels

This is the author accepted manuscript. The final version is available from the publisher via the DOI in this record.We present here the measurement of the diffusivity of spherical particles closely confined by narrow microchannels. Our experiments yield a two-dimensional map of the position-dependent diffusion coefficients parallel and perpendicular to the channel axis with a resolution down to 129 nm. The diffusivity was measured simultaneously in the channel interior, the bulk reservoirs, as well as the channel entrance region. In the channel interior we found strongly anisotropic diffusion. While the perpendicular diffusion coefficient close to the confining walls decreased down to approximately 25% of the value on the channel axis, the parallel diffusion coefficient remained constant throughout the entire channel width. In addition to the experiment, we performed finite element simulations for the diffusivity in the channel interior and found good agreement with the measurements. Our results reveal the distinctive influence of strong confinement on Brownian motion, which is of significance to microfluidics as well as quantitative models of facilitated membrane transport.S.L.D. acknowledges funding from the German Academic Exchange Service (DAAD) and the German National Academic Foundation. S.P. and U.F.K. were supported by an ERC starting grant. S.P. also acknowledges support from the Leverhulme Trust and the Newton Trust through an Early Career Fellowship

Phase Fluctuations in Bose-Einstein Condensates

We demonstrate the existence of phase fluctuations in elongated Bose-Einstein Condensates (BECs) and study the dependence of those fluctuations on the system parameters. A strong dependence on temperature, atom number, and trapping geometry is observed. Phase fluctuations directly affect the coherence properties of BECs. In particular, we observe instances where the phase coherence length is significantly smaller than the condensate size. Our method of detecting phase fluctuations is based on their transformation into density modulations after ballistic expansion. An analytic theory describing this transformation is developed.Comment: 11 pages, 7 figure

Localization and Anomalous Transport in a 1-D Soft Boson Optical Lattice

We study the dynamics of Bose-Einstein condensed atoms in a 1-D optical lattice potential in a regime where the collective (Josephson) tunneling energy is comparable with the on-site interaction energy, and the number of particles per lattice site is mesoscopically large. By directly imaging the motion of atoms in the lattice, we observe an abrupt suppression of atom transport through the array for a critical ratio of these energies, consistent with quantum fluctuation induced localization. Directly below the onset of localization, the frequency of the observed superfluid transport can be explained by a phonon excitation but deviates substantially from that predicted by the hydrodynamic/Gross-Pitaevskii equations.Comment: 14 pages, 5 figure

A rare low-grade myofibroblastic sarcoma in lower jaw with the resemblance to benign lesions.

BACKGROUND Low-grade myofibroblastic sarcoma (LGMS) is a rare solid infiltrative soft tissue tumor with a predilection for the head and neck region. CASE PRESENTATION We report the diagnostic steps of a fast-growing lesion of the lower left jaw in a 45-year-old otherwise healthy woman. A first biopsy and subsequent histopathological examination showed potential differentials of a benign myofibroma, benign nodular fasciitis or an LGMS. This diagnostic overlap was a challenge for the decision of the further treatment approach. The treatment consisted of a segmental en bloc resection of the mandible including the second premolar, first and second molar. Histopathological examination of the resected tumor confirmed an LGMS. CONCLUSION The histopathologic resemblance of LGMS to a range of benign and reactive tumors may lead to misdiagnosis and mistreatment. The rarity of LGMS explains the lack of established treatment protocols. This case shows the importance of adequate clinical decisions, expertise in the histopathology of rare tumors and interdisciplinary exchange to achieve state-of-the-art patient management

Cribriform Morular Thyroid Carcinoma - Ultimobranchial Pouch-Related? Deep Molecular Insights of a Unique Case.

A 44-year-old female patient with a familial adenomatous polyposis (FAP) was diagnosed with a cribriform morular thyroid carcinoma (CMTC). We observed within the very necrotic tumor a small but distinct poorly differentiated carcinomatous component. As expected, next generation sequencing of both components revealed a homozygous APC mutation and in addition, a TERT promoter mutation. A TP53 mutation was found exclusively in the CMTC part, while the poorly differentiated component showed a clonal evolution, harboring an activating PIK3CA mutation and copy number gains of BRCA2, FGF23, FGFR1, and PIK3CB-alterations which are typically seen in squamous cell carcinoma. The mutational burden in both components was low, and there was no evidence for microsatellite instability. No mutations involving the mitogen-activated protein kinase (MAPK) pathway, typically seen in papillary thyroid carcinomas, were detected. Immunohistochemically, all tumor parts were negative for thyroglobulin, providing further evidence that this entity does not belong to the follicular epithelial cell-derived thyroid carcinoma group. CD5 was negative in the poorly differentiated component, making a relation to intrathyroidal thymic carcinoma rather unlikely. However, since this marker was seen in the morules, a loss in the poorly differentiated component and a relation to the ultimobranchial body cannot be excluded either. After total thyroidectomy and radioiodine ablation, the patient was disease-free with no residual tumor burden on 2-year follow-up

Adaptable-radius, time-orbiting magnetic ring trap for Bose-Einstein condensates

We theoretically investigate an adjustable-radius magnetic storage ring for laser-cooled and Bose-condensed atoms. Additionally, we discuss a novel time-dependent variant of this and other ring traps. Time-orbiting ring traps provide a high optical access method for spin-flip loss prevention near a storage ring's circular magnetic field zero. Our scalable storage ring will allow one to probe the fundamental limits of condensate Sagnac interferometry.Comment: 5 pages, 3 figures. accepted in J Phys