We studied the transmission of positronium through thin graphene films supported with lacy carbon using an energy-tunable positronium beam recently developed based on photodetachment of positronium ...negative ions. By analysing the results of the measurements conducted with different number of graphene layers, the transmittance per single-layer graphene without lacy carbon was estimated to be 70% and 74% at 2.3 keV and 3.3 keV, respectively.
Graphical Abstract
We demonstrate here that cold antihydrogen beams formed and extracted from a cusp magnet (anti-Helmholtz coils) are well focused and spin-polarized. A new discovery was the fact that the antihydrogen ...beam follows the well-known lens formula of optical lenses with its focal length properly scaled with the initial kinetic energy, the magnetic field strength and the magnetic moment. Furthermore, the simulation revealed that for a certain kinetic energy region of antihydrogen atoms, the optimum production position is upstream of the center of the cusp magnet, where a well-known nested potential configuration can be applied.
We have developed a torsion balance to detect the rotation of a cell containing spin-polarized gaseous atoms to study angular momentum transfer from gaseous atoms to solid. A cesium vapor cell was ...hung from a thin wire in a vacuum chamber, and irradiated from the bottom with circularly polarized light tuned to the D2 transition to polarize cesium atoms in the cell. By varying the light helicity at the resonance frequency of the torsion balance, we induced forced rotational oscillation of the cell and detected radiation torque exerted on the cesium vapor cell through the cesium atoms inside. The torque was particularly large when both hyperfine levels of cesium atoms were optically pumped with application of a longitudinal magnetic field. Further detailed study will provide new insights into spin-transfer processes at the gas-solid interface.
We investigated the optical and magnetic properties of a transparent magnetic garnet with a particular focus on its applications to atomic physics experiments. The garnet film used in this study was ...a magnetically soft material that was originally designed for a Faraday rotator at optical communication wavelengths in the near infrared region. The film had a thickness of 2.1 μm and a small optical loss at a wavelength of
λ
=
780
nm resonant with Rb atoms. The Faraday effect was also small and, thus, barely affected the polarization of light at
λ
=
780
nm. In contrast, large Faraday rotation angles at shorter wavelengths enabled us to visualize magnetic domains, which were perpendicularly magnetized in alternate directions with a period of 3.6 μm. We confirmed the generation of an evanescent wave on the garnet film, which can be used for the optical observation and manipulation of atoms on the surface of the film. Finally, we demonstrated a magnetic mirror for laser-cooled Rb atoms using the garnet film.
Threshold photodetachment spectroscopy of the positronium negative ion has been accomplished for the first time employing an efficient source of the ions and photodetachment techniques combined with ...a tunable optical parametric oscillator and amplifier laser. The photodetachment threshold, corresponding to the electron affinity of positronium (13S1), was determined to be 326.88 ± 0.09 (stat) ± 0.10 (syst) meV by laser photodetachment threshold measurements. This result is consistent with a variational calculation corrected for leading relativistic and quantum electrodynamical effects.
View support is one of the most attractive features of relational databases from both theoretical and practical points of view. However, as views are not base relations stored in a database but ...merely definitions of queries issued to a database, the updatability of views poses a difficult dilemma known as the view update problem. To resolve the problem, many theoretical investigations, namely, the syntactic, semantic, interactive, and intention-based approaches were conducted, with the intention-based approach being the most promising. In practice, SQL-92 standardized a necessary and sufficient condition for updatable views, but its updatability is limited. Although new criteria for updatable views were standardized in SQL:1999, its implementation seemed to be hard. To benefit relational database users, we aimed to implement the intention-based approach for a relational database management system. However, we faced two issues in doing so. Therefore, in this study, we present the positive solutions to these problems. First, as theoretical works are based on set semantics and SQL standards on bag semantics, whether the intention-based approach can be extended to bag semantics or not should be investigated. Second, the approach should be implemented on PostgreSQL, which is the prevalent open source relational database management system in the world.
In daily interaction with others, we can behave cooperatively by estimating the intention of others and predicting their behavior. It is important to understand the mechanism of such smooth ...cooperative behavior for both comprehending human social cognitive ability and designing social artifacts that can interact with humans. To clarify effective functions that constitute the mechanism, we constructed a computational model of cooperative behavior in which an action decision process is dynamically controlled based on an estimation of intention of other. The model estimates the other's intention from his⁄her behavior by reusing the knowledge of one's own action decisions. However, in a condition in which agents mutually estimate the intentions of others, the cooperation performance is unsatisfactory. We addressed the problem by introducing “level” of estimation. Our model combines three types of action decision strategies: an action strategy based on the estimation of other's intention, one based on the estimation of one's own intention by other, and an action strategy that doesn't use the intention of other. To analyze the model, we simulated tasks in which two hunters cooperatively chased two preys and demonstrated that this model achieved smooth cooperation. The result suggests the effectiveness of our model.
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