372 research outputs found
Clear Experimental Signature of Charge-Orbital density wave in NdCaMnO
Single Crystals of NdCaMnO have been prepared by the
travelling floating-zone method, and possible evidence of a charge -orbital
density wave in this material presented earlier [PRB68,092405 (2003)] using
High Resolution Electron Microscopy [HRTEM] and Electron Diffraction [ED]. In
the current note we present direct evidence of charge-orbital ordering in this
material using heat capacity measurements. Our heat capacity measurements
indicate a clear transition consistent with prior observation. We find two main
transitions, one at temperature K, and other at
K. In addition, we may also conclude that there is a strong electron-phonon
coupling in this material.Comment: 7 pages, 8 figure
Electrodeposition of Zinc-Telluride Compound Semiconductors
Zinc-telluride compound semiconductors were electrodeposited from acidic aqueous solution. Under potential deposition (UPD) of zinc was observed during the co-deposition of zinc and tellurium. UPD of zinc was promoted by rising the solution temperature up to 353K. Band gap energy of annealed zinc-telluride films with almost ideal stoichiometric composition (Zn:Te=1:1) were close to 2.26 eV.Nagasaki Symposium on Nano-Dynamics 2008 (NSND2008) 平成20年1月29日(火)於長崎大学 Poster Presentatio
10-kJ PW Laser for the FIREX-I Program
A 10-kJ PW laser (LFEX) is under construction for the
FIREX-I program. This paper reports a design overview of LFEX, the
technological development of a large-aperture arrayed amplifier with
modified four-pass architecture, wavefront correction, a large-aperture
Faraday rotator with a superconducting magnet, a new pulse compressor
arrangement, and focus control
Electronic structure of the strongly hybridized ferromagnet CeFe2
We report on results from high-energy spectroscopic measurements on CeFe2, a
system of particular interest due to its anomalous ferromagnetism with an
unusually low Curie temperature and small magnetization compared to the other
rare earth-iron Laves phase compounds. Our experimental results indicate very
strong hybridization of the Ce 4f states with the delocalized band states,
mainly the Fe 3d states. In the interpretation and analysis of our measured
spectra, we have made use of two different theoretical approaches: The first
one is based on the Anderson impurity model, with surface contributions
explicitly taken into account. The second method consists of band-structure
calculations for bulk CeFe2. The analysis based on the Anderson impurity model
gives calculated spectra in good agreement with the whole range of measured
spectra, and reveals that the Ce 4f -- Fe 3d hybridization is considerably
reduced at the surface, resulting in even stronger hybridization in the bulk
than previously thought. The band-structure calculations are ab initio
full-potential linear muffin-tin orbital calculations within the
local-spin-density approximation of the density functional. The Ce 4f electrons
were treated as itinerant band electrons. Interestingly, the Ce 4f partial
density of states obtained from the band-structure calculations also agree well
with the experimental spectra concerning both the 4f peak position and the 4f
bandwidth, if the surface effects are properly taken into account. In addition,
results, notably the partial spin magnetic moments, from the band-structure
calculations are discussed in some detail and compared to experimental findings
and earlier calculations.Comment: 10 pages, 8 figures, to appear in Phys. Rev. B in December 200
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Enhancing laser beam performance by interfering intense laser beamlets
Increasing the laser energy absorption into energetic particle beams represents a longstanding quest in intense laser-plasma physics. During the interaction with matter, part of the laser energy is converted into relativistic electron beams, which are the origin of secondary sources of energetic ions, γ-rays and neutrons. Here we experimentally demonstrate that using multiple coherent laser beamlets spatially and temporally overlapped, thus producing an interference pattern in the laser focus, significantly improves the laser energy conversion efficiency into hot electrons, compared to one beam with the same energy and nominal intensity as the four beamlets combined. Two-dimensional particle-in-cell simulations support the experimental results, suggesting that beamlet interference pattern induces a periodical shaping of the critical density, ultimately playing a key-role in enhancing the laser-to-electron energy conversion efficiency. This method is rather insensitive to laser pulse contrast and duration, making this approach robust and suitable to many existing facilities
On-orbit Operations and Offline Data Processing of CALET onboard the ISS
The CALorimetric Electron Telescope (CALET), launched for installation on the
International Space Station (ISS) in August, 2015, has been accumulating
scientific data since October, 2015. CALET is intended to perform long-duration
observations of high-energy cosmic rays onboard the ISS. CALET directly
measures the cosmic-ray electron spectrum in the energy range of 1 GeV to 20
TeV with a 2% energy resolution above 30 GeV. In addition, the instrument can
measure the spectrum of gamma rays well into the TeV range, and the spectra of
protons and nuclei up to a PeV.
In order to operate the CALET onboard ISS, JAXA Ground Support Equipment
(JAXA-GSE) and the Waseda CALET Operations Center (WCOC) have been established.
Scientific operations using CALET are planned at WCOC, taking into account
orbital variations of geomagnetic rigidity cutoff. Scheduled command sequences
are used to control the CALET observation modes on orbit. Calibration data
acquisition by, for example, recording pedestal and penetrating particle
events, a low-energy electron trigger mode operating at high geomagnetic
latitude, a low-energy gamma-ray trigger mode operating at low geomagnetic
latitude, and an ultra heavy trigger mode, are scheduled around the ISS orbit
while maintaining maximum exposure to high-energy electrons and other
high-energy shower events by always having the high-energy trigger mode active.
The WCOC also prepares and distributes CALET flight data to collaborators in
Italy and the United States.
As of August 31, 2017, the total observation time is 689 days with a live
time fraction of the total time of approximately 84%. Nearly 450 million events
are collected with a high-energy (E>10 GeV) trigger. By combining all operation
modes with the excellent-quality on-orbit data collected thus far, it is
expected that a five-year observation period will provide a wealth of new and
interesting results.Comment: 11 pages, 7 figures, published online 27 February 201
Search for GeV Gamma-ray Counterparts of Gravitational Wave Events by CALET
We present results on searches for gamma-ray counterparts of the LIGO/Virgo
gravitational-wave events using CALorimetric Electron Telescope ({\sl CALET})
observations. The main instrument of {\sl CALET}, CALorimeter (CAL), observes
gamma-rays from GeV up to 10 TeV with a field of view of nearly 2 sr.
In addition, the {\sl CALET} gamma-ray burst monitor (CGBM) views 3 sr
and sr of the sky in the 7 keV -- 1 MeV and the 40 keV -- 20 MeV
bands, respectively, by using two different crystal scintillators. The {\sl
CALET} observations on the International Space Station started in October 2015,
and here we report analyses of events associated with the following
gravitational wave events: GW151226, GW170104, GW170608, GW170814 and GW170817.
Although only upper limits on gamma-ray emission are obtained, they correspond
to a luminosity of erg s in the GeV energy band
depending on the distance and the assumed time duration of each event, which is
approximately the order of luminosity of typical short gamma-ray bursts. This
implies there will be a favorable opportunity to detect high-energy gamma-ray
emission in further observations if additional gravitational wave events with
favorable geometry will occur within our field-of-view. We also show the
sensitivity of {\sl CALET} for gamma-ray transient events which is the order of
~erg\,cm\,s for an observation of 100~s duration.Comment: 12 pages, 8 figures, 1 table. Accepted for publication in
Astrophysical Journa
Effective three-band model for double perovskites
We start from a six-band model describing the transition-metal t2g orbitals
of half-metallic double perovskite systems, such as Sr2FeMoO6, in which only
one of the transition metal ions (Fe) contains important intratomic repulsion
Ufe. By eliminating the Mo orbitals using a low-energy reduction similar to
that used in the cuprates, we construct a Hamiltonian which contains only
effective t2g Fe orbitals. This allows to treat exactly Ufe, and most of the
Fe-Mo hopping. As an application, we treat the effective Hamiltonian in the
slave-boson mean-field approximation and calculate the position of the
metal-insulator transition and other quantities as a function of pressure or
on-site energy difference.Comment: 8 pages, 3 figure
Successful Treatment for Hepatic Encephalopathy Aggravated by Portal Vein Thrombosis with Balloon-Occluded Retrograde Transvenous Obliteration
This report presents the case of a 78-year-old female with hepatic encephalopathy due to an inferior mesenteric venous-inferior vena cava shunt. She developed hepatocellular carcinoma affected by hepatitis C virus-related cirrhosis and underwent posterior sectionectomy. Portal vein thrombosis developed and the portal trunk was narrowed after hepatectomy. Portal vein thrombosis resulted in high portal pressure and increased blood flow in an inferior mesenteric venous-inferior vena cava shunt, and hepatic encephalopathy with hyperammonemia was aggravated. The hepatic encephalopathy aggravated by portal vein thrombosis was successfully treated by balloon-occluded retrograde transvenous obliteration via a right transjugular venous approach without the development of other collateral vessels
CALET results after three years on the International Space Station
The CALET (CALorimetric Electron Telescope) space experiment, which is currently conducting direct cosmic-ray observations onboard the International Space Station (ISS), is an all-calorimetric instrument optimized for cosmic-ray electron measurements with capability to measure hadrons and gamma-rays. Since the start of observation in October 2015, smooth and continuous operations have taken place. In this paper, we will give a brief summary of the CALET observations ranging from charged cosmic rays, gamma-rays, to space weather, while focusing on the energy spectra of electrons and protons
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