2,206 research outputs found
A detector for continuous measurement of ultra-cold atoms in real time
We present the first detector capable of recording high-bandwidth real time
atom number density measurements of a Bose Einstein condensate. Based on a
two-color Mach-Zehnder interferometer, our detector has a response time that is
six orders of magnitude faster than current detectors based on CCD cameras
while still operating at the shot-noise limit. With this minimally destructive
system it may be possible to implement feedback to stabilize a Bose-Einstein
condensate or an atom laser.Comment: 3 pages, 3 figures, submitted to optics letter
From multimode to monomode guided atom lasers: an entropic analysis
We have experimentally demonstrated a high level of control of the mode
populations of guided atom lasers (GALs) by showing that the entropy per
particle of an optically GAL, and the one of the trapped Bose Einstein
condensate (BEC) from which it has been produced are the same. The BEC is
prepared in a crossed beam optical dipole trap. We have achieved isentropic
outcoupling for both magnetic and optical schemes. We can prepare GAL in a
nearly pure monomode regime (85 % in the ground state). Furthermore, optical
outcoupling enables the production of spinor guided atom lasers and opens the
possibility to tailor their polarization
An FPGA-based controller for collaborative robotics
The use of robots is becoming more common in society. Industrial robots are being developed to work with people, and lower-force collaborative robots are being developed to help people in their everyday lives. These may need fast and sophisticated motion control and behavioral algorithms, but are expected to be more compact and lower cost. This paper proposes a processor plus FPGA solution for the control systems for such robots, where the FPGA performs all real-time tasks, freeing the processor to run lower-frequency high level control and interface to other devices such as camera systems. A demonstrator robot is designed, combining multi-axis motion control with 3D robot vision
Optical waveform sampling of a 320 Gbits/s serial data signal using a hydrogenated amorphous silicon waveguide
We propose using a hydrogenated amorphous silicon waveguide for ultra-high-speed serial data waveform sampling. 320 Gbit/s serial optical data sampling is experimentally demonstrated with +12 dB intrinsic four wave mixing conversion efficiency
A multibeam atom laser: coherent atom beam splitting from a single far detuned laser
We report the experimental realisation of a multibeam atom laser. A single
continuous atom laser is outcoupled from a Bose-Einstein condensate (BEC) via
an optical Raman transition. The atom laser is subsequently split into up to
five atomic beams with slightly different momenta, resulting in multiple,
nearly co-propagating, coherent beams which could be of use in interferometric
experiments. The splitting process itself is a novel realization of Bragg
diffraction, driven by each of the optical Raman laser beams independently.
This presents a significantly simpler implementation of an atomic beam
splitter, one of the main elements of coherent atom optics
Crowdfunding as Donations to Entrepreneurial Firms
The bulk of today's (“preorder-,” “reward-,” “gift-,” and “donation-based”) crowdfunding raises funds for small, private entrepreneurial ventures without granting funders private claims to the projects’ income or the ability to guarantee the realization and delivery of project outcomes. We theorize and show empirically – via a mixed-method approach applied to a representative and remarkably informative case – that the payoff structure for crowdfunders, akin to a public good contribution problem, leads to the tangible value of main project outputs exerting little influence on contributions to crowdfunding. This then raises the question of which funder motivations fund seekers may have to address to crowdfund their projects. We demonstrate the especially large role of non-pecuniary motivations and pinpoint three particular motivations that profit-seeking entrepreneurs may stimulate to be financed through crowdfunding. The findings hold important implications for entrepreneurs’ crowdfunding strategies, platform design, and our understanding of how this funding institution works in general. The study also adds to emerging research on the implications of the public good nature of crowdfunding
Synthesis and Recognition Properties of Higher Order Tetrathiafulvalene (Ttf) Calix N Pyrroles (N=4-6)
Two new benzoTTF-annulated calix[n]pyrroles (n = 5 and 6) were synthesized via a one-step acid catalyzed condensation reaction and fully characterized via single crystallographic analyses. As compared to the known tetra-TTF annulated calix[4]pyrrole, which is also produced under the conditions of the condensation reaction, the expanded calix[n]pyrroles (n = 5 and 6) are characterized by a larger cavity size and a higher number of TTF units (albeit the same empirical formula). Analysis of the binding isotherms obtained from UV-Vis spectroscopic titrations carried out in CHCl3 in the presence of both anionic (Cl-, Br-, I-, CH3COO-, H2PO4-, and HSO4-) and neutral (1,3,5-trinitrobenzene (TNB) and 2,4,6-trinitrotoluene (TNT)) substrates revealed that as a general rule the calix[6]pyrrole derivative proved to be the most efficient molecular receptor for anions, while the calix[4]pyrrole congener proves most effective for the recognition of TNB and TNT. These findings are rationalized in terms of the number of electron rich TTF subunits and NH hydrogen bond donor groups within the series, as well as an ability to adopt conformations suitable for substrate recognition, and are supported by solid state structural analyses.National Science Foundation CHE 1057904, 0741973Robert A. Welch Foundation F-1018Danish Natural Science Research Council (FNU) 272-08-0047, 11-106744WCU (World Class University) program of Korea R32-2010-10217-0Villum FoundationChemistr
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