3,297 research outputs found
Predictability of reset switching voltages in unipolar resistance switching
In unipolar resistance switching of NiO capacitors, Joule heating in the
conducting channels should cause a strong nonlinearity in the low resistance
state current-voltage (I-V) curves. Due to the percolating nature of the
conducting channels, the reset current IR, can be scaled to the nonlinear
coefficient Bo of the I-V curves. This scaling relationship can be used to
predict reset voltages, independent of NiO capacitor size; it can also be
applied to TiO2 and FeOy capacitors. Using this relation, we developed an error
correction scheme to provide a clear window for separating reset and set
voltages in memory operations
Direct observation of the proliferation of ferroelectric loop domains and vortex-antivortex pairs
We discovered "stripe" patterns of trimerization-ferroelectric domains in
hexagonal REMnO3 (RE=Ho, ---, Lu) crystals (grown below ferroelectric
transition temperatures (Tc), reaching up to 1435 oC), in contrast with the
vortex patterns in YMnO3. These stripe patterns roughen with the appearance of
numerous loop domains through thermal annealing just below Tc, but the stripe
domain patterns turn to vortex-antivortex domain patterns through a freezing
process when crystals cross Tc even though the phase transition appears not to
be Kosterlitz-Thouless-type. The experimental systematics are compared with the
results of our six-state clock model simulation and also the Kibble-Zurek
Mechanism for trapped topological defects
DNA hypomethylation and germ cell-specific expression of testis-specific H2B histone gene
Testis-specific H2B (TH2B) histone gene of rat is expressed during meiotic event of spermatogenic differentiation. The gene is unusual in that it has conserved the regulatory elements involved in the S phase-specific transcription of somatic H2B genes as well as the S phase-specific stabilization of histone mRNA. Genomic sequencing revealed that all analyzed CpG sites in the promoter region of TH2B gene are methylated in somatic tissues but not in testis. During spermatogenesis, these CpG sites are unmethylated as early as spermatogonia type A and up to sperm. Thus, there is a good correlation between DNA hypomethylation and germ cell-specific expression of TH2B gene. Results obtained from in vivo DNase footprinting and DNA mobility shift experiments are consistent with the hypothesis that DNA methylation inhibits gene activity by preventing the binding of transcription factors to their recognition sequences. The results show that (i) the binding of ubiquitous transcription factors to the promoter region of TH2B gene may be blocked in nuclei of liver, and (ii) DNA methylation can directly interfere with the binding of transcription factors recognizing a hexamer (ACGTCA) motif. In vitro DNA methylation and transfection experiments demonstrated that expression of TH2B gene is inhibited by DNA methylation in vivo. These findings indicate that DNA methylation may play a key role in the transcriptional repression of germ cell-specific TH2B gene
Granular Scale Magnetic Flux Cancellations in the Photosphere
We investigate the evolution of 5 granular-scale magnetic flux cancellations
just outside the moat region of a sunspot by using accurate spectropolarimetric
measurements and G-band images with the Solar Optical Telescope aboard Hinode.
The opposite polarity magnetic elements approach a junction of the
intergranular lanes and then they collide with each other there. The
intergranular junction has strong red shifts, darker intensities than the
regular intergranular lanes, and surface converging flows. This clearly
confirms that the converging and downward convective motions are essential for
the approaching process of the opposite-polarity magnetic elements. However,
motion of the approaching magnetic elements does not always match with their
surrounding surface flow patterns in our observations. This suggests that, in
addition to the surface flows, subsurface downward convective motions and
subsurface magnetic connectivities are important for understanding the approach
and collision of the opposite polarity elements observed in the photosphere. We
find that the horizontal magnetic field appears between the canceling opposite
polarity elements in only one event. The horizontal fields are observed along
the intergranular lanes with Doppler red shifts. This cancellation is most
probably a result of the submergence (retraction) of low-lying photospheric
magnetic flux. In the other 4 events, the horizontal field is not observed
between the opposite polarity elements at any time when they approach and
cancel each other. These approaching magnetic elements are more concentrated
rather than gradually diffused, and they have nearly vertical fields even while
they are in contact each other. We thus infer that the actual flux cancellation
is highly time dependent events at scales less than a pixel of Hinode SOT
(about 200 km) near the solar surface.Comment: Accepted for publication in the Astrophysical Journa
On Propagation Characteristics of Reconfigurable Surface Wave Platform: Simulation and Experimental Verification
Reconfigurable intelligent surface (RIS) as a smart reflector is
revolutionizing research for next-generation wireless communications.
Complementing this is a concept of using RIS as an efficient propagation medium
for potentially superior path loss characteristics. Motivated by a recent
porous surface architecture that facilitates reconfigurable pathways with
cavities filled with fluid metal, this paper studies the propagation
characteristics of different pathway configurations in different lossy
materials on the reconfigurable surface wave platform by using a commercial
full electromagnetic simulation software and S-parameters experiments. This
paper also looks into the best scheme to switch between a straight pathway and
a -bend and attempts to quantify the additional path loss when making
a turn. Our experimental results verify the simulation results, showing the
effectiveness of the proposed reconfigurable surface wave platform for a
wide-band, low path loss and highly programmable communications.Comment: Submitted to IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, 202
Improved Iterative Coordinated Beamforming Based on Singular Value Decomposition for Multiuser Mimo Systems With Limited Feedforward
Coordinated beamforming based on singular value decomposition is an iterative method to jointly optimize thetransmit beamformers and receive combiners, to achieve high levels of sum rates in the downlink of multiusersystems, by exploiting the multi-dimensional wireless channel created by multiple transmit and receive antennas. The optimization is done at the base station and the quantized beamformers are sent to the users through a low rate link.In this work, we propose to optimize this algorithm by reducing the number of iterations and improving its uncoded bit error rate performance. Simulation results show that our proposal achieves a better bit error rate with a lower number of iterations than the original algorithm
Strong lens search in the ESO public Survey KiDS
We have started a systematic search of strong lens candidates in the ESO
public survey KiDS based on the visual inspection of massive galaxies in the
redshift range . As a pilot program we have inspected 100 sq. deg.,
which overlap with SDSS and where there are known lenses to use as a control
sample. Taking advantage of the superb image quality of VST/OmegaCAM, the
colour information and accurate model subtracted images, we have found 18 new
lens candidates, for which spectroscopic confirmation will be needed to confirm
their lensing nature and study the mass profile of the lensing galaxies.Comment: 4 pages, 1 figure, to appear on the refereed Proceeding of the "The
Universe of Digital Sky Surveys" conference held at the INAF--OAC, Naples, on
25th-28th november 2014, to be published on Astrophysics and Space Science
Proceedings, edited by Longo, Napolitano, Marconi, Paolillo, Iodic
Functional complementarity between the HMG1-like yeast mitochondrial histone HM and the bacterial histone-like protein HU
The mitochondrial histone HM is the major DNA-binding protein in mitochondria and is necessary for maintenance of the mitochondrial genome in the yeast Saccharomyces cerevisiae during growth on fermentable sugars. HM and the Escherichia coli histone-like protein HU have similar activities in vitro, including DNA supercoiling, but share no sequence similarity. We show that HU can functionally complement the respiration deficiency associated with yeast strains lacking HM. Conversely, phenotypes of E. coli cells lacking HU protein, including nucleoid loss and a filamentous cell morphology, were alleviated by expression of HM in these cells. The HU protein of bacteria and the HM protein of mitochondria are therefore functionally complementary in vivo. Functional similarities among HM, HU, and the nuclear HMG1 proteins are implicated and discussed
Specific regions of the intervening sequences of beta-globin RNA are resistant to nuclease in 50S heterogeneous nuclear RNA-protein complexes.
The specific assembly of heterogeneous nuclear RNA-protein complexes (hnRNPs) containing precursor beta-globin RNA was investigated by using the 50S hnRNP released from chicken reticulocyte nuclei by endogenous nuclease. The nuclease-resistant regions were mapped on adult beta-globin intervening sequences (IVS) at the resolution of nucleotides with an RNA mapping method [Patton, J. R. and Chae, C.-B. (1983) J. Biol. Chem. 258, 3991-3995]. We found that there is one 28-nucleotide-long nuclease-resistant region in the first IVS and there are four nuclease-resistant regions in the second IVS. Of particular interest is the presence in 50S hnRNP of a nuclease-resistant region (24-28 nucleotides long) in both IVS immediately upstream from the putative lariat branch site in an RNA splicing intermediate. Our results demonstrate that hnRNPs containing precursor beta-globin RNA are, like those containing mature beta-globin RNA, assembled in a site-specific manner
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