562,503 research outputs found
Direct visualization of aging in colloidal glasses
We use confocal microscopy to directly visualize the dynamics of aging
colloidal glasses. We prepare a colloidal suspension at high density, a simple
model system which shares many properties with other glasses, and initiate
experiments by stirring the sample. We follow the motion of several thousand
colloidal particles after the stirring and observe that their motion
significantly slows as the sample ages. The aging is both spatially and
temporally heterogeneous. Furthermore, while the characteristic relaxation time
scale grows with the age of the sample, nontrivial particle motions continue to
occur on all time scales.Comment: submitted to proceedings for Liquid Matter Conference 200
Direct visualization of magnetic vortex pinning in superconductors
We study the vortex structure in a Pb film deposited on top of a periodic
array of ferromagnetic square microrings by combining two high resolution
imaging techniques: Bitter decoration and scanning Hall probe microscopy
(SHPM). The periodicity and strength of the magnetic pinning potential
generated by the square microrings are controlled by the magnetic history of
the template. When the square rings are in the magnetized dipolar state, known
as the onion state, the strong stray field generated at the domain walls
prevents the decoration of vortices. SHPM images show that the stray field
generated by the dipoles is much stronger than the vortex field in agreement
with the results of simulations. Real space vortex imaging has revealed that,
in the onion state, the corners of the square rings act as effective pinning
centers for vortices.Comment: To be published in Phys. Rev.
Direct Visualization of Laser-Driven Focusing Shock Waves
Cylindrically or spherically focusing shock waves have been of keen interest
for the past several decades. In addition to fundamental study of materials
under extreme conditions, cavitation, and sonoluminescence, focusing shock
waves enable myriad applications including hypervelocity launchers, synthesis
of new materials, production of high-temperature and high-density plasma
fields, and a variety of medical therapies. Applications in controlled
thermonuclear fusion and in the study of the conditions reached in laser fusion
are also of current interest. Here we report on a method for direct real-time
visualization and measurement of laser-driven shock generation, propagation,
and 2D focusing in a sample. The 2D focusing of the shock front is the
consequence of spatial shaping of the laser shock generation pulse into a ring
pattern. A substantial increase of the pressure at the convergence of the
acoustic shock front is observed experimentally and simulated numerically.
Single-shot acquisitions using a streak camera reveal that at the convergence
of the shock wave in liquid water the supersonic speed reaches Mach 6,
corresponding to the multiple gigapascal pressure range 30 GPa
VolumeEVM: A new surface/volume integrated model
Volume visualization is a very active research area in the field of scien-tific
visualization. The Extreme Vertices Model (EVM) has proven to be
a complete intermediate model to visualize and manipulate volume data
using a surface rendering approach. However, the ability to integrate the
advantages of surface rendering approach with the superiority in visual exploration
of the volume rendering would actually produce a very complete
visualization and edition system for volume data. Therefore, we decided
to define an enhanced EVM-based model which incorporates the volumetric
information required to achieved a nearly direct volume visualization
technique. Thus, VolumeEVM was designed maintaining the same EVM-based
data structure plus a sorted list of density values corresponding to
the EVM-based VoIs interior voxels. A function which relates interior
voxels of the EVM with the set of densities was mandatory to be defined.
This report presents the definition of this new surface/volume integrated
model based on the well known EVM encoding and propose implementations
of the main software-based direct volume rendering techniques
through the proposed model.Postprint (published version
The vortex at an inlet of an air intake
Vortex at air intake inlet investigated by direct air flow visualization technique
Change in Working Length at Different Stages of Instrumentation as a Function of Canal Curvature
The aim of this study was to determine the change in working length (∆WL) before and after coronal flaring and after complete rotary instrumentation as a function of canal curvature. One mesiobuccal or mesiolingual canal from each of 43 extracted molars had coronal standardization and access performed. Once the access was completed, canal preparation was accomplished using Gates Glidden drills for coronal flaring and EndoSequence files for rotary instrumentation. WLs were obtained at 3 time points: pre-instrumentation (unflared), mid-instrumentation (flared) and post-instrumentation (concluded). Measurements were made via direct visualization (DV) and the CanalPro apex locator (EM) in triplicate by a single operator with blinding within the time points. Root curvature was measured using Schneider’s technique. The change in working length was assessed using repeated-measures ANCOVA. The direct visualization measurements were statistically larger than the electronic measurements (paired t-test difference = 0.20 mm, SE = 0.037, P \u3c .0001), although a difference this large may not be clinically important. Overall, a greater change in working length was observed in straight canals than in curved canals, and this trend was more pronounced when measured electronically than via direct visualization, especially in the unflared-concluded time points compared with unflared-flared time points. A greater change in working length was also observed in longer canals than in shorter canals.https://scholarscompass.vcu.edu/gradposters/1032/thumbnail.jp
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