162 research outputs found
Resonant Control of Interaction Between Different Electronic States
We observe a magnetic Feshbach resonance in a collision between the ground
and metastable states of two-electron atoms of ytterbium (Yb). We measure the
on-site interaction of doubly-occupied sites of an atomic Mott insulator state
in a three-dimensional optical lattice as a collisional frequency shift in a
high-resolution laser spectroscopy. The observed spectra are well fitted by a
simple theoretical formula, in which two particles with an s-wave contact
interaction are confined in a harmonic trap. This analysis reveals a wide
variation of the interaction with a resonance behavior around a magnetic field
of about 1.1 Gauss for the energetically lowest magnetic sublevel of
Yb, as well as around 360 mG for the energetically highest magnetic
sublevel of Yb. The observed Feshbach resonance can only be induced
by an anisotropic inter-atomic interaction. This novel scheme will open the
door to a variety of study using two-electron atoms with tunable interaction.Comment: 5 pages, 5 figure
Unmanned aerial vehicles and deep learning for assessment of anthropogenic marine debris on beaches on an island in a semi-enclosed sea in Japan
The increasing prevalence of marine debris is a global problem, and urgent action for amelioration is needed. Identifying hotspots where marine debris accumulates will enable effective control; however, knowledge on the location of accumulation hotspots remains incomplete. In particular, marine debris accumulation on beaches is a concern. Surveys of beaches require intensive human effort, and survey methods are not standardized. If marine debris monitoring is conducted using a standardized method, data from different regions can be compared. With an unmanned aerial vehicle (UAV) and deep learning computational methods, monitoring a wide area at a low cost in a standardized way may be possible. In this study, we aimed to identify marine debris on beaches through deep learning using high-resolution UAV images by conducting a survey on Narugashima Island in the Seto Inland Sea of Japan. The flight altitude relative to the ground was set to 5 m, and images of a 0.81-ha area were obtained. Flight was conducted twice: before and after the beach cleaning. The combination of UAVs equipped with a zoom lens and operation at a low altitude allows for the acquisition of high resolution images of 1.1 mm/pixel. The training dataset (2970 images) was annotated by using VoTT, categorizing them into two classes: 'anthropogenic marine debris' and 'natural objects.' Using RetinaNet, marine debris was identified with an average sensitivity of 51% and a precision of 76%. In addition, the abundance and area of marine debris coverage were estimated. In this study, it was revealed that the combination of UAVs and deep learning enables the effective identification of marine debris. The effects of cleanup activities by citizens were able to be quantified. This method can widely be used to evaluate the effectiveness of citizen efforts toward beach cleaning and low-cost long-term monitoring
Multi-state interferometric measurement of nonlinear AC Stark shift
We demonstrate measurement of quadratic AC Stark shifts between Zeeman
sublevels in an Rb Bose--Einstein condensate using a multi-state atomic
interferometer. The interferometer can detect a quadratic shift without being
affected by relatively large state-independent shifts, thereby improving the
measurement precision. We measure quadratic shifts in the total spin
state due to the light being near-resonant to the D line. The agreement
between the measured and theoretical detuning dependences of the quadratic
shifts confirms the validity of the measurement. We also present results on the
suppression of nonlinear spin evolution using near-resonant dual-color light
pulses with opposite quadratic shifts.Comment: 7 pages, 6 figure
Do Kepler superflare stars really include slowly-rotating Sun-like stars ? - Results using APO 3.5m telescope spectroscopic observations and Gaia-DR2 data -
We report the latest view of Kepler solar-type (G-type main-sequence)
superflare stars, including recent updates with Apache Point Observatory (APO)
3.5m telescope spectroscopic observations and Gaia-DR2 data. First, we newly
conducted APO3.5m spectroscopic observations of 18 superflare stars found from
Kepler 1-min time cadence data. More than half (43 stars) are confirmed to be
"single" stars, among 64 superflare stars in total that have been
spectroscopically investigated so far in this APO3.5m and our previous
Subaru/HDS observations. The measurements of (projected rotational
velocity) and chromospheric lines (Ca II H\&K and Ca II 8542\AA) support the
brightness variation of superflare stars is caused by the rotation of a star
with large starspots. We then investigated the statistical properties of Kepler
solar-type superflare stars by incorporating Gaia-DR2 stellar radius estimates.
As a result, the maximum superflare energy continuously decreases as the
rotation period increases. Superflares with energies
erg occur on old, slowly-rotating Sun-like stars
(25 days) approximately once every 2000--3000 years,
while young rapidly-rotating stars with a few days have
superflares up to erg. The maximum starspot area does not depend on
the rotation period when the star is young, but as the rotation slows down, it
starts to steeply decrease at 12 days for Sun-like
stars. These two decreasing trends are consistent since the magnetic energy
stored around starspots explains the flare energy, but other factors like spot
magnetic structure should also be considered.Comment: 71 pages, 31 figures, 10 tables. Accepted for publication in The
Astrophysical Journal (on March 29, 2019
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