Saturation of Cs2 Photoassociation in an Optical Dipole Trap

We present studies of strong coupling in single-photon photoassociation of cesium dimers using an optical dipole trap. A thermodynamic model of the trap depletion dynamics is employed to extract absolute rate coefficents. From the dependence of the rate coefficient on the photoassociation laser intensity, we observe saturation of the photoassociation scattering probability at the unitarity limit in quantitative agreement with the theoretical model by Bohn and Julienne [Phys. Rev. A, 60, 414 (1999)]. Also the corresponding power broadening of the resonance width is measured. We could not observe an intensity dependent light shift in contrast to findings for lithium and rubidium, which is attributed to the absence of a p or d-wave shape resonance in cesium

Nanopore SimulatION – a raw data simulator for Nanopore Sequencing

Nanopore DNA sequencing enables the sequence determination of single DNA molecules up to 10,000 times longer than currently permitted by second-generation sequencing platforms. Nanopore sequencing gives real-time access to sequencing data and enables the detection of epigenetic modifications. This unique feature set is poised to foster the development of novel biomedical applications previously deemed unfeasible. Nanopore sequencing is based on picoampere scale measurement of current modulated by DNA or RNA polymers traveling through a nanometer opening between two compartments. Each of the five canonical nucleobases (A, T, G, C, U) has a characteristic electrical resistance, which ultimately enables the determination of the precise base sequence. However, a substantial computational effort is required to resolve the underlying sequence from a time-warped and noisy stream of digitized current measurements. Recently, a wide range of digital signal analysis and machine learning methods have been developed for Nanopore sequencing applications. Clinically relevant questions, such as the quantification of short repetitive DNA sequences remain an unresolved challenge to current generic, state-of-the-art nanopore data analysis methods. We believe realistic simulation of the signal stream can be instrumental in the development of tailored algorithms for such novel biomedical applications. Based on our work with the Oxford Nanopore Technologies MinION and PromethION platform, we have developed Nanopore SimulatION, a software package for the in silico generation of realistic, raw-signal-level data. Nanopore SimulatION starts from a reference genome in conjunction with a configuration and model file derived from real-world nanopore sequencing experiments as input. To validate our algorithm, we have sequenced custom synthetic DNA, and in so doing have generated a “ground-truth” data set potentially useful for downstream algorithm development. Additionally, we demonstrate Nanopore SimulatION` s utility for method development in typical clinical use cases

The minimum period problem in cataclysmic variables

We investigate if consequential angular momentum losses (CAML) or an intrinsic deformation of the donor star in CVs could increase the CV bounce period from the canonical theoretical value ~65 min to the observed value $P_{min} \approx77$ min, and if a variation of these effects in a CV population could wash out the theoretically predicted accumulation of systems near the minimum period (the period spike). We are able to construct suitably mixed CV model populations that a statisticial test cannot rule out as the parent population of the observed CV sample. However, the goodness of fit is never convincing, and always slightly worse than for a simple, flat period distribution. Generally, the goodness of fit is much improved if all CVs are assumed to form at long orbital periods. The weighting suggested by King, Schenker & Hameury (2002) does not constitute an improvment if a realistically shaped input period distribution is used. Put your abstract here.Comment: 10 pages, Latex, 13 postscript figures, Accepted for publication in MNRA

Sympathetic Cooling with Two Atomic Species in an Optical Trap

We simultaneously trap ultracold lithium and cesium atoms in an optical dipole trap formed by the focus of a CO$_2$ laser and study the exchange of thermal energy between the gases. The cesium gas, which is optically cooled to $20 \mu$K, efficiently decreases the temperature of the lithium gas through sympathetic cooling. The measured cross section for thermalizing $^{133}$Cs-$^7$Li collisions is $8 \times 10^{-12}$ cm$^2$, for both species in their lowest hyperfine ground state. Besides thermalization, we observe evaporation of lithium purely through elastic cesium-lithium collisions (sympathetic evaporation).Comment: 4 pages 3 fig

Inkjet-printed stretchable and low voltage synaptic transistor array.

Wearable and skin electronics benefit from mechanically soft and stretchable materials to conform to curved and dynamic surfaces, thereby enabling seamless integration with the human body. However, such materials are challenging to process using traditional microelectronics techniques. Here, stretchable transistor arrays are patterned exclusively from solution by inkjet printing of polymers and carbon nanotubes. The additive, non-contact and maskless nature of inkjet printing provides a simple, inexpensive and scalable route for stacking and patterning these chemically-sensitive materials over large areas. The transistors, which are stable at ambient conditions, display mobilities as high as 30 cm2 V-1 s-1 and currents per channel width of 0.2 mA cm-1 at operation voltages as low as 1 V, owing to the ionic character of their printed gate dielectric. Furthermore, these transistors with double-layer capacitive dielectric can mimic the synaptic behavior of neurons, making them interesting for conformal brain-machine interfaces and other wearable bioelectronics