8,263 research outputs found
Particle-Based Microfluidic Device for Providing High Magnetic Field Gradients
A microfluidic device for manipulating particles in a fluid has a device body that defines a main channel therein, in which the main channel has an inlet and an outlet. The device body further defines a particulate diverting channel therein, the particulate diverting channel being in fluid connection with the main channel between the inlet and the outlet of the main channel and having a particulate outlet. The microfluidic device also has a plurality of microparticles arranged proximate or in the main channel between the inlet of the main channel and the fluid connection of the particulate diverting channel to the main channel. The plurality of microparticles each comprises a material in a composition thereof having a magnetic susceptibility suitable to cause concentration of magnetic field lines of an applied magnetic field while in operation. A microfluidic particle-manipulation system has a microfluidic particle-manipulation device and a magnet disposed proximate the microfluidic particle-manipulation device
MCViNE -- An object oriented Monte Carlo neutron ray tracing simulation package
MCViNE (Monte-Carlo VIrtual Neutron Experiment) is a versatile Monte Carlo
(MC) neutron ray-tracing program that provides researchers with tools for
performing computer modeling and simulations that mirror real neutron
scattering experiments. By adopting modern software engineering practices such
as using composite and visitor design patterns for representing and accessing
neutron scatterers, and using recursive algorithms for multiple scattering,
MCViNE is flexible enough to handle sophisticated neutron scattering problems
including, for example, neutron detection by complex detector systems, and
single and multiple scattering events in a variety of samples and sample
environments. In addition, MCViNE can take advantage of simulation components
in linear-chain-based MC ray tracing packages widely used in instrument design
and optimization, as well as NumPy-based components that make prototypes useful
and easy to develop. These developments have enabled us to carry out detailed
simulations of neutron scattering experiments with non-trivial samples in
time-of-flight inelastic instruments at the Spallation Neutron Source. Examples
of such simulations for powder and single-crystal samples with various
scattering kernels, including kernels for phonon and magnon scattering, are
presented. With simulations that closely reproduce experimental results,
scattering mechanisms can be turned on and off to determine how they contribute
to the measured scattering intensities, improving our understanding of the
underlying physics.Comment: 34 pages, 14 figure
Effect of Spatial Charge Inhomogeneity on 1/f Noise Behavior in Graphene
Scattering mechanisms in graphene are critical to understanding the limits of
signal-to-noise-ratios of unsuspended graphene devices. Here we present the
four-probe low frequency noise (1/f) characteristics in back-gated single layer
graphene (SLG) and bilayer graphene (BLG) samples. Contrary to the expected
noise increase with the resistance, the noise for SLG decreases near the Dirac
point, possibly due to the effects of the spatial charge inhomogeneity. For
BLG, a similar noise reduction near the Dirac point is observed, but with a
different gate dependence of its noise behavior. Some possible reasons for the
different noise behavior between SLG and BLG are discussed.Comment: 28 pages, 3 figures + 3 supplement figure
Fast non-negative deconvolution for spike train inference from population calcium imaging
Calcium imaging for observing spiking activity from large populations of
neurons are quickly gaining popularity. While the raw data are fluorescence
movies, the underlying spike trains are of interest. This work presents a fast
non-negative deconvolution filter to infer the approximately most likely spike
train for each neuron, given the fluorescence observations. This algorithm
outperforms optimal linear deconvolution (Wiener filtering) on both simulated
and biological data. The performance gains come from restricting the inferred
spike trains to be positive (using an interior-point method), unlike the Wiener
filter. The algorithm is fast enough that even when imaging over 100 neurons,
inference can be performed on the set of all observed traces faster than
real-time. Performing optimal spatial filtering on the images further refines
the estimates. Importantly, all the parameters required to perform the
inference can be estimated using only the fluorescence data, obviating the need
to perform joint electrophysiological and imaging calibration experiments.Comment: 22 pages, 10 figure
Size-controlled synthesis of monodispersed gold nanoparticles via carbon monoxide gas reduction
An in depth analysis of gold nanoparticle (AuNP) synthesis and size tuning, utilizing carbon monoxide (CO) gas as a reducing agent, is presented for the first time. The sizes of the AuNPs are tunable from ~4 to 100 nm by altering the concentration of HAuCl4 and inlet CO gas-injection flow rate. It is also found that speciation of aqueous HAuCl4, prior to reduction, influences the size, morphology, and properties of AuNPs when reduced with CO gas. Ensemble extinction spectra and TEM images provide clear evidence that CO reduction offers a high level of monodispersity with standard deviations as low as 3%. Upon synthesis, no excess reducing agent remains in solution eliminating the need for purification. The time necessary to synthesize AuNPs, using CO, is less than 2 min
Extended Line Emission in the BCG of Abell 2390
We report CFHT/SITELLE imaging Fourier Transform Spectrograph observations of
the Brightest Cluster Galaxy (BCG) of galaxy cluster Abell 2390 at z=0.228. The
BCG displays a prominent cone of emission in H, H, [NII], and
[OII] to the North-West with PA = 42, 4.4 arcsec in length (15.9 kpc),
which is associated with elongated and asymmetric Chandra soft X-ray emission.
The H flux map also contains a "hook" of H and [NII] emission
resulting in a broadened northern edge to the cone. Using SITELLE/LUCI software
we extract emission line flux, velocity, velocity dispersion, and continuum
maps, and utilize them to derive flux ratio maps to determine ionization
mechanisms and dynamical information in the BCG's emission line region. The
Baldwin-Phillips-Terlevich diagnostics on the BCG cone indicate a composite
ionization origin of photoionization due to star formation and shock. Strong
LINER-like emission is seen in the nuclear region which hosts an AGN. As Abell
2390 is a cool-core cluster, we suggest that the cooling flow is falling onto
the central BCG and interacting with the central AGN. The AGN produces jets
that inflate "bubbles" of plasma in the ICM, as is often observed in local
galaxy clusters. Furthermore, combining signs of AGN activities from radio,
optical emission line and X-ray data over a large range of physical scale, we
find evidence for three possible episodes of AGN activity in different epochs
associated with the Abell 2390 BCG.Comment: 15 pages, 13 figures, accepted by MNRA
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