2,074 research outputs found
Charge-noise-free Lateral Quantum Dot Devices with Undoped Si/SiGe Wafer
We develop quantum dots in a single layered MOS structure using an undoped
Si/SiGe wafer. By applying a positive bias on the surface gates, electrons are
accumulated in the Si channel. Clear Coulomb diamond and double dot charge
stability diagrams are measured. The temporal fluctuation of the current is
traced, to which we apply the Fourier transform analysis. The power spectrum of
the noise signal is inversely proportional to the frequency, and is different
from the inversely quadratic behavior known for quantum dots made in doped
wafers. Our results indicate that the source of charge noise for the doped
wafers is related to the 2DEG dopant.Comment: Proceedings of the 12th Asia Pacific Physics Conferenc
Mantle earthquakes frozen in mylonitized ultramafic pseudotachylytes of spinel-lherzolite facies.
We report a new type of ultramafi c pseudotachylyte that forms a fault- and injection-vein
network hosted in the mantle-derived Balmuccia peridotite (Italy). In the fault vein the pseudotachylyte
is now deformed and recrystallized into a spinel-lherzolite facies ultramylonite, made
of a fi ne (<2 μm) aggregate of olivine, orthopyroxene, clinopyroxene, and spinel, with small
amounts of amphibole and dolomite. Electron backscattered diffraction study of the ultramylonite
shows a clear crystallographic preferred orientation (CPO) of olivine. The fault vein
pseudotachylyte overprints a spinel-lherzolite facies amphibole-bearing mylonite, indicating
that shear localization accompanying chemical reaction had taken place in the peridotite before
seismic slip produced frictional melting. The occurrence of amphibole in the host mylonite and
that of dolomite as well as amphibole in the matrices of ultramylonite and pseudotachylyte may
indicate that fl uid was present and had evolved in its composition from H2O-rich to CO2-rich
during ductile deformation with metamorphic reactions, which may account for the observed
rheological transition from ductile to brittle behavior. The spinel-lherzolite facies assemblage
in mylonites, P-T estimations from pyroxene geothermometry and carbonate reactions, and
the type of olivine CPO in deformed pseudotachylyte indicate that both the preseismic and the
postseismic ductile deformations occurred at ~800 °C and 0.7–1.1 GPa
Spin-Echo Measurements for an Anomalous Quantum Phase of 2D Helium-3
Previous heat-capacity measurements of our group had shown the possible
existence of an anomalous quantum phase containing the zero-point vacancies
(ZPVs) in 2D He. The system is monolayer He adsorbed on graphite
preplated with monolayer He at densities () just below the 4/7
commensurate phase (). We carried out
pulsed-NMR measurements in order to examine the microscopic and dynamical
nature of this phase. The measured decay of spin echo signals shows the
non-exponential behaviour. The decay curve can be fitted with the double
exponential function, but the relative intensity of the component with a longer
time constant is small (5%) and does not depend on density and temperature,
which contradicts the macroscopic fluid and 4/7 phase coexistence model. This
slowdown is likely due to the mosaic angle spread of Grafoil substrate and the
anisotropic spin-spin relaxation time in 2D systems with respect to the
magnetic field direction. The inverse value deduced from the major echo
signal with a shorter time constant, which obeys the single exponential
function, decreases linearly with decreasing density from , supporting the
ZPV model.Comment: 4 pages, 6 figure
Coherent Manipulation of Individual Electron Spin in a Double Quantum Dot Integrated with a Micro-Magnet
We report the coherent manipulation of electron spins in a double quantum dot
integrated with a micro-magnet. We performed electric dipole spin resonance
experiments in the continuous wave (CW) and pump-and-probe modes. We observed
two resonant CW peaks and two Rabi oscillations of the quantum dot current by
sweeping an external magnetic field at a fixed frequency. Two peaks and
oscillations are measured at different resonant magnetic field, which reflects
the fact that the local magnetic fields at each quantum dot are modulated by
the stray field of a micro-magnet. As predicted with a density matrix approach,
the CW current is quadratic with respect to microwave (MW) voltage while the
Rabi frequency (\nu_Rabi) is linear. The difference between the \nu_Rabi values
of two Rabi oscillations directly reflects the MW electric field across the two
dots. These results show that the spins on each dot can be manipulated
coherently at will by tuning the micro-magnet alignment and MW electric field.Comment: 5 pages, 3 figure
Suppression of cell cycle progression by Jun dimerization protein (JDP2) involves down-regulation of cyclin A2
We report here a novel role for Jun dimerization protein-2 (JDP2) as a regulator of the progression of normal cells through the cell cycle. To determine the role of JDP2 in vivo, we generated Jdp2 knock-out (Jdp2KO) mice by targeting exon 1 to disrupt the site of initiation of transcription. The healing of wounded skin of Jdp2KO mice proceeded more rapidly than that of control mice and more proliferating cells were found at wound margins. Fibroblasts derived from embryos of Jdp2KO mice proliferated more rapidly and formed more colonies than wild-type fibroblasts. JDP2 was recruited to the promoter of the gene for cyclin A2 (ccna2) at a previously unidentified AP-1 site. Cells lacking Jdp2 had elevated levels of cyclin A2 mRNA. Moreover, reintroduction of JDP2 resulted in repression of transcription of ccna2 and of cell cycle progression. Thus, transcription of the gene for cyclin A2 appears to be a direct target of JDP2 in the suppression of cell proliferation
Spectral cross-calibration of VIIRS enhanced vegetation index with MODIS: A case study using year-long global data
© 2015 by the authors; licensee MDPI, Basel, Switzerland. In this study, the Visible Infrared Imaging Radiometer Suite (VIIRS) Enhanced Vegetation Index (EVI) was spectrally cross-calibrated with the Moderate Resolution Imaging Spectroradiometer (MODIS) EVI using a year-long, global VIIRS-MODIS dataset at the climate modeling grid (CMG) resolution of 0.05°-by-0.05°. Our cross-calibration approach was to utilize a MODIS-compatible VIIRS EVI equation derived in a previous study [Obata et al., J. Appl. Remote Sens., vol.7, 2013] and optimize the coefficients contained in this EVI equation for global conditions. The calibrated/optimized MODIS-compatible VIIRS EVI was evaluated using another global VIIRS-MODIS CMG dataset of which acquisition dates did not overlap with those used in the calibration. The calibrated VIIRS EVI showed much higher compatibility with the MODIS EVI than the original VIIRS EVI, where the mean error (MODIS minus VIIRS) and the root mean square error decreased from -0.021 to -0.003 EVI units and from 0.029 to 0.020 EVI units, respectively. Error reductions on the calibrated VIIRS EVI were observed across nearly all view zenith and relative azimuth angle ranges, EVI dynamic range, and land cover types. The performance of the MODIS-compatible VIIRS EVI calibration appeared limited for high EVI values (i.e., EVI > 0.5) due likely to the maturity of the VIIRS dataset used in calibration/optimization. The cross-calibration methodology introduced in this study is expected to be useful for other spectral indices such as the normalized difference vegetation index and two-band EVI
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