555 research outputs found
A New Reduced Basis Method for Parabolic Equations Based on Single-Eigenvalue Acceleration
In this paper, we develop a new reduced basis (RB) method, named as Single
Eigenvalue Acceleration Method (SEAM), for second-order parabolic equations
with homogeneous Dirichlet boundary conditions. The high-fidelity numerical
method adopts the backward Euler scheme and conforming finite elements for the
temporal and spatial discretization, respectively. Under the assumption that
the time step size is sufficiently small and time steps are not very large, we
show that the singular value distribution of the high-fidelity solution matrix
is close to that of a rank one matrix. We select the eigenfunction
associated with the principal eigenvalue of the matrix as the basis
of the Proper Orthogonal Decomposition (POD) method to obtain SEAM and a
parallel SEAM. Numerical experiments confirm the efficiency of the new method
Preparation and characterization of antigenic properties of gramicidin A- keyhole limpet hemocyanin and gramicidin A- ovalbumin conjugates
A rapid, simple and low cost procedure for preparing hapten-protein conjugates was developed using gramicidin A (GA) and two other water-soluble proteins, keyhole limpet hemocyanin (KLH) and ovalbumin (OVA). GA was a kind of antimicrobial peptides. Two lysines and a cysteine were linked to amino- terminus and carboxyl-terminus of the peptide chain, respectively, in order to form sulfhydryl groups and improve its water solubility. And the molecule weight and purity of the modified peptidechain were checked by electron spray ionization mass spectrometry (ESI-MS) and high performance liquid chromatography (HPLC). Then the activated KLH and OVA were conjugated to GA by using 4-(Nmaleimidomethyl) cyclohexane-1-carboxylic acid 3-sulfo-N-hydroxysuccinimide ester sodium salt (sulfo-SMCC) to form disulfide linkage. In order to obtain artificial antigen of GA, GA was linked to KLHand OVA by sulfo-SMCC coupling at room temperature. The conjugates of KLH-Peptide and OVAPeptide were identified by infrared and ultraviolet spectrophotometry SDS-PAGE and DTNB method, which could prove the activity of the sulfhydryl-groups. In this way, we have obtained a novel artificial immunogen and coating antigen that could be used to raise polyclonal antibody through immunized rabbits
Lidar with Velocity: Correcting Moving Objects Point Cloud Distortion from Oscillating Scanning Lidars by Fusion with Camera
Lidar point cloud distortion from moving object is an important problem in
autonomous driving, and recently becomes even more demanding with the emerging
of newer lidars, which feature back-and-forth scanning patterns. Accurately
estimating moving object velocity would not only provide a tracking capability
but also correct the point cloud distortion with more accurate description of
the moving object. Since lidar measures the time-of-flight distance but with a
sparse angular resolution, the measurement is precise in the radial measurement
but lacks angularly. Camera on the other hand provides a dense angular
resolution. In this paper, Gaussian-based lidar and camera fusion is proposed
to estimate the full velocity and correct the lidar distortion. A probabilistic
Kalman-filter framework is provided to track the moving objects, estimate their
velocities and simultaneously correct the point clouds distortions. The
framework is evaluated on real road data and the fusion method outperforms the
traditional ICP-based and point-cloud only method. The complete working
framework is open-sourced
(https://github.com/ISEE-Technology/lidar-with-velocity) to accelerate the
adoption of the emerging lidars
Ultrafast Charge Transfer in Atomically Thin MoS2/WS2 Heterostructures
Van der Waals heterostructures have recently emerged as a new class of
materials, where quantum coupling between stacked atomically thin
two-dimensional (2D) layers, including graphene, hexagonal-boron nitride, and
transition metal dichalcogenides (MX2), give rise to fascinating new phenomena.
MX2 heterostructures are particularly exciting for novel optoelectronic and
photovoltaic applications, because 2D MX2 monolayers can have an optical
bandgap in the near-infrared to visible spectral range and exhibit extremely
strong light-matter interactions. Theory predicts that many stacked MX2
heterostructures form type-II semiconductor heterojunctions that facilitate
efficient electron-hole separation for light detection and harvesting. Here we
report the first experimental observation of ultrafast charge transfer in
photo-excited MoS2/WS2 heterostructures using both photoluminescence mapping
and femtosecond (fs) pump-probe spectroscopy. We show that hole transfer from
the MoS2 layer to the WS2 layer takes place within 50 fs after optical
excitation, a remarkable rate for van der Waals coupled 2D layers. Such
ultrafast charge transfer in van der Waals heterostructures can enable novel 2D
devices for optoelectronics and light harvesting
Systematic Determination of Absolute Absorption Cross-section of Individual Carbon Nanotubes
Determination of optical absorption cross-section is always among the central
importance of understanding a material. However its realization on individual
nanostructures, such as carbon nanotubes, is experimentally challenging due to
the small extinction signal using conventional transmission measurements. Here
we develop a technique based on polarization manipulation to enhance the
sensitivity of single-nanotube absorption spectroscopy by two-orders of
magnitude. We systematically determine absorption cross-section over broad
spectral range at single-tube level for more than 50 chirality-defined
single-walled nanotubes. Our data reveals chirality-dependent one-dimensional
photo-physics through the behaviours of exciton oscillator strength and
lifetime. We also establish an empirical formula to predict absorption spectrum
of any nanotube, which provides the foundation to determine quantum
efficiencies in important photoluminescence and photovoltaic processes
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