689 research outputs found
14-08 Big Data Analytics to Aid Developing Livable Communities
In transportation, ubiquitous deployment of low-cost sensors combined with powerful computer hardware and high-speed network makes big data available. USDOT defines big data research in transportation as a number of advanced techniques applied to the capture, management and analysis of very large and diverse volumes of data. Data in transportation are usually well organized into tables and are characterized by relatively low dimensionality and yet huge numbers of records. Therefore, big data research in transportation has unique challenges on how to effectively process huge amounts of data records and data streams. The purpose of this study is to conduct research on the problems caused by large data volume and data streams and to develop applications for data analysis in transportation. To process large number of records efficiently, we have proposed to aggregate the data at multiple resolutions and to explore the data at various resolutions to balance between accuracy and speed. Techniques and algorithms in statistical analysis and data visualization have been developed for efficient data analytics using multiresolution data aggregation. Results will be helpful in setting up a primitive stage towards a rigorous framework for general analytical processing of big data in transportation
Symbol-Aided Approach to Nonlinear Distortion Cancellation for Self-Heterodyne OFDM Direct Conversion Receivers
We propose a symbol-aided approach to nonlinear
distortion cancellation and data demodulation in self-heterodyne
direct conversion (SHDC) receivers for discrete Fourier
transform (DFT)-based orthogonal frequency division
multiplexing (OFDM) systems. In order to cancel the
intermodulation distortion generated at the square-law device
output in the receiver, the SHDC transmitter generates an
OFDM symbol followed by the next symbols having a phase
difference of 90 degree. By using this approach, quadrature
modulation can be supported with direct conversion. The
advantages of the proposed technique are demonstrated through
the computer simulation
Radiative Transfer in Ly{\alpha} Nebulae: I. Modeling a Continuous or Clumpy Spherical Halo with a Central Source
To understand the mechanism behind high- Ly nebulae, we simulate
the scattering of Ly in a halo about a central
Ly source. For the first time, we consider both smooth and clumpy
distributions of halo gas, as well as a range of outflow speeds, total column densities, spatial concentrations, and central source
galaxies (e.g., with Ly line widths corresponding to those typical of
AGN or star-forming galaxies). We compute the spatial-frequency diffusion and
the polarization of the Ly photons scattered by atomic hydrogen. Our
scattering-only model reproduces the typical size of Ly nebulae
(kpc) at total column densities and predicts a range of positive, flat, and negative polarization
radial gradients. We also find two general classes of Ly nebula
morphologies: with and without bright cores. Cores are seen when
is low, i.e., when the central source is directly visible, and are associated
with a polarization jump, a steep increase in the polarization radial profile
just outside the halo center. Of all the parameters tested in our smooth or
clumpy medium model, dominates the trends. The radial behaviors of
the Ly surface brightness, spectral line shape, and polarization in
the clumpy model with covering factor approach those of the
smooth model at the same . A clumpy medium with high
and low generates Ly features via scattering that
the smooth model cannot: a bright core, symmetric line profile, and
polarization jump.Comment: 42 pages, 27 figures, accepted for publication in ApJ, Comments
welcome
Dimensional reduction, quantum Hall effect and layer parity in graphite films
The quantum Hall effect (QHE) originates from discrete Landau levels forming
in a two-dimensional (2D) electron system in a magnetic field. In three
dimensions (3D), the QHE is forbidden because the third dimension spreads
Landau levels into multiple overlapping bands, destroying the quantisation.
Here we report the QHE in graphite crystals that are up to hundreds of atomic
layers thick - thickness at which graphite was believed to behave as a 3D bulk
semimetal. We attribute the observation to a dimensional reduction of electron
dynamics in high magnetic fields, such that the electron spectrum remains
continuous only in the direction of the magnetic field, and only the last two
quasi-one-dimensional (1D) Landau bands cross the Fermi level. In sufficiently
thin graphite films, the formation of standing waves breaks these 1D bands into
a discrete spectrum, giving rise to a multitude of quantum Hall plateaux.
Despite a large number of layers, we observe a profound difference between
films with even and odd numbers of graphene layers. For odd numbers, the
absence of inversion symmetry causes valley polarisation of the standing-wave
states within 1D Landau bands. This reduces QHE gaps, as compared to films of
similar thicknesses but with even layer numbers because the latter retain the
inversion symmetry characteristic of bilayer graphene. High-quality graphite
films present a novel QHE system with a parity-controlled valley polarisation
and intricate interplay between orbital, spin and valley states, and clear
signatures of electron-electron interactions including the fractional QHE below
0.5 K
Enhanced Electrokinetic Transport of Sulfate in Saline Soil
The electrokinetic transport of sulfate was investigated as a means of treating and restoring a sulfate-accumulating saline soil. The electrokinetic treatment decreased the electrical conductivity of the soil, an indicator of soil salinity, to 58.6%, 73.1%, and 83.5% for 7, 14 and 21 days, respectively. More than 96% of the chloride and nitrate were removed within 7 days. However, the removal of sulfate was highly influenced by the anode material. An iron anode removed sulfate effectively, whereas, sulfate was hyper-accumulated in the anodic region when an inert anode was used. The iron anode was oxidized in a sacrificial anodic reaction, which competed with the electrolysis reaction of water at the anode, and finally the reaction prevented the severe acidification of the soil in the anodic region. However, the competing reactions produced hydrogen ions at the anode, and the ions were transported toward the cathode, which, in turn, acidified the soil, especially, in the anodic region. The acidification switched the surface charge of the soil from negative to positive, increasing the interaction between the soil surface and sulfate, and thus inhibiting the transport of sulfate under the electric field. The zeta potential analysis of the soil provided an explanation. The results indicate that preventing severe acidification is an important factor which influences the transport of anions and iron anode for the enhanced removal of anionic pollutants by electrokinetic remediation
Mid-term results in patients having tricuspidization of the quadricuspid aortic valve
BACKGROUND: Quadricuspid aortic valve (QAV) is a rare congenital anomaly. We investigate the mid-term results of aortic valve reconstruction by tricuspidization in patients with QAV. METHODS: We analyzed the outcome of eight consecutive patients who underwent aortic valve reconstruction surgery (AVRS) with pericardial leaflets with symptomatic quadricuspid aortic valve (QAV) disease between December 2007 and May 2012. AVRS consists of leaflet reconstruction and fixation of the sino-tubular junction in order to maintain coaptation of the new valve. RESULTS: Six males and two females were included; ages ranged from 19 to 63 years (mean age, 51 years). According to Hurwitz and Roberts’s classification, three patients had type A, three patients had type B, one patient had type C, and one patient had type E. All patients had significant aortic regurgitation (AR): moderate in three patients, moderate to severe in one patient, and severe in four patients. Concomitant ascending aorta wrapping with an artificial vascular graft was performed in one case. There was no occurrence of mortality during the follow-up period (42.4 ± 18.0 months). No redo-operation was required. The NYHA functional class showed improvement from 2.1 ± 0.2 to 1.1 ± 0.2 (p = 0.008). The latest echocardiograms showed AR absent or trivial in seven patients, and mild in one patient. The aortic valve orifice area index (AVAI) was 1.03 ± 0.49 cm(2)/m(2). Compared with preoperative echocardiograms, the left ventricular (LV) ejection fraction showed improvement from 57.6 ± 17.0 to 63.7 ± 13.2% (p = 0.036); the end-diastolic and end-systolic LV dimensions showed a significant decrease, from 63.5 ± 9.6 to 49.5 ± 3.1 mm (p = 0.012) and 43.6 ± 11.8 to 32.1 ± 5.4 mm (p = 0.012), respectively. CONCLUSION: In patients with QAV, AVRS with tricuspidization showed satisfactory early and mid-term results. Long-term follow-up will be necessary in order to study the durability of AVRS; however, it can be considered as a potential standard procedure
Fluoxetine Up-Regulates Bcl-xL Expression in Rat C6 Glioma Cells
Objective To analyze both differentially expressed genes and the Bcl-xL protein expression after acute and chronic treatment with fluoxetine in rat C6 glioma cells. Methods C6 glioma cells were cultured for 24 h or 72 h after treatment with 10 mu M fluoxetine, and gene expression patterns were observed using microarray and qRT-PCR. Then, cells were cultured for 6 h, 24 h, 72 h or 96 h after treatment with 10 mu M fluoxetine, and the expression of Bd-xL protein was measured using western blot. Results As determined by microarray, treatment with fluoxetine for 24 h up-regulated 33 genes (including Bcl-xL and NCAM140) and down-regulated 7 genes (including cyclin G-associated kinase). Treatment with fluoxetine for 72 h up-regulated 53 genes (including Gs alpha and Bcl-xL) and down-regulated 77 genes (including Gai2 and annexin V). Based on the qRT-PCR results, there was an increase in Gsa mRNA and a decrease in G alpha i2 mRNA at 72 h in fluoxetine-treated cells as compared to control, a result that was consistent with microarray. We also observed an increase in Bcl-xL mRNA (both at 24 h and at 72 h) in fluoxetine-treated cells as compared to control, demonstrating a tendency to increase gradually. Bcl-xL protein expression increased as the duration of fluoxetine treatment increased. Conclusion These results suggest that chronic treatment with fluoxetine not only initiates the cAMP pathway through inducing Gsa expression but also induces Bcl-xL expression, thus inhibiting apoptosis. Psychiatry Investig 2011;8:161-168This work was supported by the research fund of Hanyang University (HY-2010-N)
Joint Channel Estimation and Phase Noise Suppression for OFDM Systems
The joint channel estimation and phase noise
suppression scheme for orthogonal frequency-division
multiplexing (OFDM) systems is proposed for a case where
channel estimation is needed symbol by symbol. In the proposed
scheme, channel estimation and phase noise suppression are
performed iteratively via the expectation-maximization (EM)
algorithm. The proposed algorithm mitigates the performance
degradation due to phase noise effectively while providing the
accurate channel estimate with comparatively few pilot
subcarriers so that the spectral efficiency of an OFDM system is
improved
Transcortical Alterations in Na+-K+ ATPase and Microtubule-Associated Proteins Immunoreactivity in the Rat Cortical Atrophy Model Induced by Hypoxic Ischemia
To identify the chronological transcortical
change in the contralateral hemisphere
following ischemic insults, we investigated the
changes in microtubule associated protein
(MAP) and Na+-K+ ATPase expressions in the
peri-infarct zone and contralateral hemisphere,
including the hippocampus. Two days after
hypoxic ischemia, Na+-K+ ATPase immunoreactivity
was significantly enhanced in the
contralateral cortex and was maintained up to 7
days after ischemia, whereas Na+-K+ ATPase immunoreactivity in the peri- and infarct zones
was unaffected by hypoxic ischemia. In contrast,
2 to 7 days after ischemia, MAP1A and MAP2
immunoreactivity in the ipsi- and contralateral
cortex significantly decreased, whereas in layer
V, MAP1 immunoreactivity obviously accumulated
in the neurons and their processes. In the
hippocampus, 2 days after insults both MAP1A
and MAP2 immunoreactivity was significantly
reduced within the ipsi- and contralateral
hippocampus. In the contralateral hippocampus,
however, the distribution of MAP2 immunoreactivity
recovered to the sham level 7 days
after ischemia, whereas MAP1A immunoreactive
axons remained 2 months after
ischemia. The results suggest that the unilateral
elevation of Na+-K+ ATPase immunoreactivity
reflects elevated neuronal activity. In addition,
this asymmetric hyperexcitability might play an
important role in the recovery or the
reorganization of the brain, accompanied by
transcortical changes in MAPs expression
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