5,029 research outputs found
A Field-Induced Re-Entrant Novel Phase and A Ferroelectric-Magnetic Order Coupling in HoMnO3
A re-entrant novel phase has been observed in the hexagonal ferroelectric
HoMnO3 in the presence of magnetic fields, in the temperature ranges defined by
the plateau of the dielectric constant anomaly. The dielectric plateau evolves
with fields from a narrow sharp dielectric peak at the Mn-spin rotation
transition at 32.8 K in zero magnetic field. Such a field-induced dielectric
plateau anomaly appears both in the temperature sweep at a constant field and
in the field sweep at a constant temperature without detectable hysteresis.
This is attributed to the indirect coupling between the ferroelectric and
antiferromagnetic orders, arising from an antiferromagnetic domain wall effect,
where the magnetic order parameter of the Mn subsystem has to change sign
across the ferroelectric domain wall in the compound, that influences the
ferroelectric domains via a local magnetostrictive effect
High-precision spectroscopy of ultracold molecules in an optical lattice
The study of ultracold molecules tightly trapped in an optical lattice can
expand the frontier of precision measurement and spectroscopy, and provide a
deeper insight into molecular and fundamental physics. Here we create, probe,
and image microkelvin Sr molecules in a lattice, and demonstrate
precise measurements of molecular parameters as well as coherent control of
molecular quantum states using optical fields. We discuss the sensitivity of
the system to dimensional effects, a new bound-to-continuum spectroscopy
technique for highly accurate binding energy measurements, and prospects for
new physics with this rich experimental system.Comment: 12 pages, 4 figure
Measurements of galactic cosmic ray shielding with the CRaTER instrument
[1] The Cosmic Ray Telescope for the Effects of Radiation (CRaTER) instrument aboard the Lunar Reconnaissance Orbiter has been measuring energetic charged particles from the galactic cosmic rays (GCRs) and solar particle events in lunar orbit since 2009. CRaTER includes three pairs of silicon detectors, separated by pieces of tissue-equivalent plastic that shield two of the three pairs from particles incident at the zenith-facing end of the telescope. Heavy-ion beams studied in previous ground-based work have been shown to be reasonable proxies for the GCRs when their energies are sufficiently high. That work, which included GCR simulations, led to predictions for the amount of dose reduction that would be observed by CRaTER. Those predictions are compared to flight data obtained by CRaTER in 2010–2011
CALIBRATION AND VALIDATION OF PRISM ONBOARD ALOS
This paper introduces the updated plans for sensor calibration and product validation of the Panchromatic Remote-sensing Instrument for Stereo Mapping (PRISM), which is to fly on the Advanced Land Observing Satellite (ALOS) satellite that will be launched this Japanese fiscal year. PRISM is used to derive digital elevation models (DEMs) with very high spatial resolution, which is also one of the objectives of the ALOS mission. To achieve this objective, PRISM consists of three panchromatic radiometers for forward-, nadir-, and backward-looking in the along-track direction, and acquires the images in the same orbit and at almost the same time. The geometric calibration is important in generating a highly accurate DEM with high spatial resolution by using PRISM’s triplet images. Highly accurate ground control points (GCP) are necessary to calibrate the geometric accuracy and validate the generated DEM. Collecting GCP worldwide is difficult and hard work in spite of its importance. In this paper, we describe the current plans for calibrating and validating PRISM aboard the ALOS, and in particular, our strategies for preparing GCP with evaluation items for geometric calibration, including expected problem effects regarding geometric accuracy. 1
Sensitive observations at 1.4 and 250 GHz of z > 5 QSOs
We present 1.4 and 5 GHz observations taken with the Very Large Array (VLA),
and observations at 250 GHz obtained with the Max-Planck millimeter bolometer
(MAMBO) at the IRAM 30~m telescope, of ten optically selected Quasi-stellar
Objects (QSOs) at 5.0 < z < 6.28. Four sources are detected at 1.4 GHz two of
which are radio loud and are also detected at 5 GHz. These results are roughly
consistent with there being no evolution of the radio-loud QSO fraction out to
z~6.
Three sources have been detected at 250 GHz or 350 GHz at much higher levels
than their 1.4 GHz flux densities suggesting that the observed mm emission is
likely thermal emission from warm dust, although more exotic possibilities
cannot be precluded.
The highest redshift source in our sample (J1030+0524 at z=6.28) is not
detected at 1.4 or 250 GHz, but four fairly bright radio sources (flux density
at 1.4GHz > 0.2 mJy) are detected in a 2' field centered on the QSO, including
an edge-brightened ('FRII') double radio source with an extent of about 1'.
A similar over-density of radio sources is seen in the field of the highest
redshift QSO J1148+5251. We speculate that these over-densities of radio
sources may indicate clusters along the lines-of-sight, in which case
gravitational lensing by the cluster could magnify the QSO emission by a factor
2 or so without giving rise to arcsecond-scale distortions in the optical
images of the QSOs.Comment: 25 pages, 12 figures. accepted by A
Atributos químicos de um Latossolo Amarelo sob diferentes sistemas de manejo.
O objetivo deste trabalho foi avaliar os atributos químicos de um Latossolo Amarelo sob diferentes sistemas de manejo do solo, no cerrado piauiense. Foram avaliados quatro sistemas de manejo: plantio convencional por três anos; plantio direto por três anos (PD3) e cinco anos (PD5), com uso de milheto como cultivo de cobertura; e plantio direto por nove anos (PD9), dos quais sete com uso de milheto e dois com forrageira. Utilizou-se área de cerrado nativo como referência. As amostras do solo foram coletadas em períodos chuvosos e secos, nas camadas 0,00?0,05, 0,05?0,10, 0,10?0,20 e 0,20?0,40 m, para determinação de pH, Al3+, H+Al, Ca2+, Mg2+, K+, P disponível, carbono orgânico total (COT), soma de bases (SB), capacidade de troca de cátions efetiva (t) e potencial (T), e saturação por bases (V) e por alumínio (m%). O sistema PD9 apresentou maiores valores de pH e menores de Al3+, H+Al e m%. Observaram-se maiores valores de Ca2+, K+, SB, t, T, V e P sob PD5 e PD9, até 0,20 m. Os maiores valores de COT foram verificados sob PD5 e PD9, exceto na camada de 0,00?0,05 m. O acúmulo de material orgânico associado ao uso de forrageira em PD favorece o aumento dos teores de COT nas camadas mais profundas do solo, no período seco
Atributos químicos de um Latossolo Amarelo sob diferentes sistemas de manejo.
O objetivo deste trabalho foi avaliar os atributos químicos de um Latossolo Amarelo sob diferentes sistemas de manejo do solo, no cerrado piauiense. Foram avaliados quatro sistemas de manejo: plantio convencional por três anos; plantio direto por três anos (PD3) e cinco anos (PD5), com uso de milheto como cultivo de cobertura; e plantio direto por nove anos (PD9), dos quais sete com uso de milheto e dois com forrageira. Utilizou-se área de cerrado nativo como referência. As amostras do solo foram coletadas em períodos chuvosos e secos, nas camadas 0,00?0,05, 0,05?0,10, 0,10?0,20 e 0,20?0,40 m, para determinação de pH, Al3+, H+Al, Ca2+, Mg2+, K+, P disponível, carbono orgânico total (COT), soma de bases (SB), capacidade de troca de cátions efetiva (t) e potencial (T), e saturação por bases (V) e por alumínio (m%). O sistema PD9 apresentou maiores valores de pH e menores de Al3+, H+Al e m%. Observaram-se maiores valores de Ca2+, K+, SB, t, T, V e P sob PD5 e PD9, até 0,20 m. Os maiores valores de COT foram verificados sob PD5 e PD9, exceto na camada de 0,00?0,05 m. O acúmulo de material orgânico associado ao uso de forrageira em PD favorece o aumento dos teores de COT nas camadas mais profundas do solo, no período seco.201
Adiabatic Domain Wall Motion and Landau-Lifshitz Damping
Recent theory and measurements of the velocity of current-driven domain walls
in magnetic nanowires have re-opened the unresolved question of whether
Landau-Lifshitz damping or Gilbert damping provides the more natural
description of dissipative magnetization dynamics. In this paper, we argue that
(as in the past) experiment cannot distinguish the two, but that
Landau-Lifshitz damping nevertheless provides the most physically sensible
interpretation of the equation of motion. From this perspective, (i) adiabatic
spin-transfer torque dominates the dynamics with small corrections from
non-adiabatic effects; (ii) the damping always decreases the magnetic free
energy, and (iii) microscopic calculations of damping become consistent with
general statistical and thermodynamic considerations
Photometric Properties of Kiso Ultraviolet-Excess Galaxies in the Lynx-Ursa Major Region
We have performed a systematic study of several regions in the sky where the
number of galaxies exhibiting star formation (SF) activity is greater than
average. We used Kiso ultraviolet-excess galaxies (KUGs) as our SF-enhanced
sample. By statistically comparing the KUG and non-KUG distributions, we
discovered four KUG-rich regions with a size of . One of these regions corresponds spatially to a filament of length
Mpc in the Lynx-Ursa Major region (). We call this ``the Lynx-Ursa
Major (LUM) filament''. We obtained surface photometry of 11 of
the KUGs in the LUM filament and used these to investigate the integrated
colors, distribution of SF regions, morphologies, and local environments. We
found that these KUGs consist of distorted spiral galaxies and compact galaxies
with blue colors. Their star formation occurs in the entire disk, and is not
confined to just the central regions. The colors of the SF regions imply that
active star formation in the spiral galaxies occurred yr ago,
while that of the compact objects occurred yr ago. Though the
photometric characteristics of these KUGs are similar to those of interacting
galaxies or mergers, most of these KUGs do not show direct evidence of merger
processes.Comment: 39 pages LaTeX, using aasms4.sty, 20 figures, ApJS accepted. The
Title of the previous one was truncated by the author's mistake, and is
corrected. Main body of the paper is unchange
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